JP7273622B2 - Power supply circuit and power supply - Google Patents

Description

The present invention relates to a power supply circuit and a power supply device.

A power supply circuit capable of generating a desired output voltage from an input voltage is mounted on various devices (see Patent Document 1, for example).

Ripple rejection is one of the important characteristics of power supply circuits. As a method of improving the ripple removal characteristic, there is a method of increasing the drive current of the power supply circuit to raise the characteristics of the circuit itself, and a method of smoothing the output voltage using a filter circuit such as an RC filter.

Japanese Patent Application Laid-Open No. 2015-201170

However, it is difficult to adopt the former method for applications that require low power consumption. According to the latter method, it is possible to achieve good ripple removal characteristics while realizing low power consumption. However, the presence of the filter circuit slows down the start-up speed of the power supply circuit (that is, it takes longer for the output voltage to reach the desired target voltage).

SUMMARY OF THE INVENTION It is an object of the present invention to provide a power supply circuit and a power supply device capable of increasing the start-up speed while maintaining good ripple removal characteristics.

A power supply circuit according to the present invention is a power supply circuit that generates a stabilized voltage from an input voltage, comprising: a first electrode for receiving the input voltage; a second electrode; an output transistor having a control electrode; supplying a control voltage to the control electrode of the output transistor based on a first node directly connected to the second electrode or connected via an insertion resistor, and a feedback voltage corresponding to the voltage of the first node; a control circuit that controls the state of the output transistor; and a filter circuit that has a filter resistor and a filter capacitor and smoothes the voltage of the first node to generate the stabilized voltage at the second node. and a charging transistor provided between the first node and the second node, the state of which is controlled based on the control voltage, wherein the charging transistor is turned on when the charging transistor is turned on. is a configuration (a first configuration) in which the filtering capacitor is charged via the .

In the power supply circuit according to the first configuration, the power supply circuit is a linear regulator that controls the output transistor so that the stabilized voltage matches a predetermined target voltage, and the control circuit controls the input voltage is lower than the target voltage, a voltage that turns on both the output transistor and the charging transistor is generated as the control voltage based on the feedback voltage, and the input voltage is lower than the target voltage. A configuration (second configuration) in which a voltage for turning on the output transistor and turning off the charging transistor based on the feedback voltage is generated as the control voltage in a predetermined second state exceeding the .

In the power supply circuit according to the first or second configuration, the output transistor and the charging transistor are configured as P-channel MOSFETs, and the first electrode, the second electrode and the control electrode of the output transistor are respectively , a source, a drain, and a gate of the output transistor, the source and the drain of the charging transistor being connected to the first node and the second node, respectively, and connected to the gates of the output transistor and the charging transistor. A configuration (third configuration) in which the control voltage is commonly applied may be employed.

In the power supply circuit according to any one of the first to third configurations, the first node is connected to the second electrode of the output transistor via the insertion resistor, and the first node and the second node are connected to each other. and a second charging transistor whose state is controlled based on the voltage drop across the insertion resistor (fourth configuration).

In the power supply circuit according to the fourth configuration, when the voltage at the second electrode of the output transistor seen from the potential of the second node is equal to or higher than the threshold voltage of the second charging transistor, the second charging The filter capacitor may be turned on to charge the filter capacitor through the second charging transistor (fifth configuration).

In the power supply circuit according to the fourth or fifth configuration, the second charging transistor is configured as an N-channel MOSFET, and the drain and source of the second charging transistor are connected to the first node, The gate of the second charging transistor connected to the second node may be connected to the second electrode of the output transistor (sixth configuration).

In the power supply circuit according to any one of the first to sixth configurations, the filter resistor is provided between the first node and the second node, and the filter resistor and the filter resistor are provided at the second node. A configuration (seventh configuration) in which the capacitors are connected to each other may also be used.

A power supply circuit according to the present invention is a power supply circuit that generates a stabilized voltage from an input voltage, comprising: a first electrode for receiving the input voltage; a second electrode; an output transistor having a control electrode; A first node connected to a second electrode via an insertion resistor, and a control voltage based on a feedback voltage corresponding to the voltage of the first node are supplied to the control electrode of the output transistor. a control circuit for controlling a state, a filter circuit having a filter resistor and a filter capacitor, and smoothing the voltage of the first node to generate the stabilized voltage at the second node; and a charging transistor provided between the second node and whose state is controlled based on the voltage drop across the insertion resistor, wherein the charging transistor is turned on when the charging transistor is turned on. A configuration (eighth configuration) in which the filter capacitor is charged via the filter capacitor may be employed.

In the power supply circuit according to the eighth configuration, the charging transistor is turned on when the voltage at the second electrode of the output transistor seen from the potential of the second node is equal to or higher than the threshold voltage of the charging transistor. A configuration (ninth configuration) in which the filtering capacitor is charged through the charging transistor in a state of

In the power supply circuit according to the eighth or ninth configuration, the charging transistor is configured as an N-channel MOSFET, and the drain and source of the charging transistor are connected to the first node and the second node, respectively. and the gate of the charging transistor is connected to the second electrode of the output transistor (tenth configuration).

In the power supply circuit according to any one of the eighth to tenth configurations, the filter resistor is provided between the first node and the second node, and the filter resistor and the filter resistor are provided at the second node. A configuration (eleventh configuration) in which the capacitors are connected to each other may also be used.

A power supply device according to the present invention comprises: a power supply circuit according to any one of the first to eleventh configurations; and a circuit (a twelfth configuration).

ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the power supply circuit and power supply device which can raise a starting speed, maintaining a favorable ripple removal characteristic.

1 is a circuit diagram of a power supply circuit according to a first embodiment of the present invention; FIG. FIG. 4 is a circuit diagram of a power supply circuit according to Example EX1_1 belonging to the first embodiment of the present invention; FIG. 10 is a diagram showing a time change of an input voltage to a power supply circuit according to example EX1_1 belonging to the first embodiment of the present invention; FIG. 10 is a diagram for explaining the behavior of the power supply circuit when the input voltage is lower than the target voltage in the power supply circuit, according to example EX1_1 belonging to the first embodiment of the present invention; FIG. 10 is a diagram for explaining the behavior of the power supply circuit when the input voltage is higher than the target voltage of the power supply circuit, according to example EX1_1 belonging to the first embodiment of the present invention; FIG. 4 is a circuit diagram of a power supply circuit according to Example EX1_2 belonging to the first embodiment of the present invention; FIG. 10 is a timing chart for explaining the operation of the power supply circuit at the start-up according to the example EX1_2 belonging to the first embodiment of the present invention; FIG. FIG. 10 is a modified circuit diagram of the power supply circuit according to example EX1_2 belonging to the first embodiment of the present invention. FIG. 4 is a circuit diagram of a power supply circuit according to Example EX1_3 belonging to the first embodiment of the present invention; FIG. 10 is a configuration diagram of a power supply device according to example EX2_1 belonging to the second embodiment of the present invention. FIG. 10 is a schematic external view of a smartphone according to example EX2_2 belonging to the second embodiment of the present invention.

Hereinafter, examples of embodiments of the present invention will be specifically described with reference to the drawings. In each figure referred to, the same parts are denoted by the same reference numerals, and redundant descriptions of the same parts are omitted in principle. In this specification, for simplification of description, by describing symbols or codes that refer to information, signals, physical quantities, elements or parts, etc., information, signals, physical quantities, elements or parts corresponding to the symbols or codes are used. etc. may be omitted or abbreviated. For example, the charging transistor referenced by "M2" below (see FIG. 2) may be written as charging transistor M2 or abbreviated as transistor M2, but they are all the same. point to something

First, an explanation is provided for some terms used in describing embodiments of the present invention. In the embodiment of the present invention, IC is an abbreviation for Integrated Circuit. The ground refers to a conductive portion having a potential of 0 V (zero volt) as a reference, or refers to a potential of 0 V itself. A potential of 0 V is sometimes referred to as a ground potential. In embodiments of the present invention, voltages shown without specific reference represent potentials with respect to ground.

For any transistor configured as a FET (Field Effect Transistor), the ON state refers to the state of conduction between the drain and the source of the transistor, and the OFF state refers to the state of conduction between the drain and the source of the transistor. is in a non-conducting state (cutoff state). The same applies to transistors that are not classified as FETs. Hereinafter, the ON state and OFF state may be simply expressed as ON and OFF.

For any MOSFETs shown below, the back gate is assumed to be connected to the source unless otherwise stated. MOSFET is an abbreviation for "metal-oxide-semiconductor field-effect transistor". MOSFETs may be understood to be enhancement-type MOSFETs unless otherwise specified. In any transistor configured as a MOSFET, the gate-to-source voltage refers to the potential of the gate relative to the potential of the source.

<<First Embodiment>>
A first embodiment of the present invention will be described. FIG. 1 is a circuit diagram of a power supply circuit 10 according to a first embodiment of the invention. The power supply circuit 10 generates a stabilized voltage as an output voltage Vout from a given input voltage Vin. The input voltage Vin is a positive DC voltage, and the target voltage Vtg of the output voltage Vout with which the output voltage Vout should match is also a positive DC voltage. The power supply circuit 10 is a step-down linear regulator, and the output voltage Vout is equal to or lower than the input voltage Vin.

The power supply circuit 10 includes an output transistor M1 configured as a P-channel MOSFET, feedback resistors R1 and R2, a filter resistor _RL and a filter capacitor _CF , a control circuit 11, Prepare. A feedback circuit is formed by the feedback resistors R1 and R2. A filter circuit FIL, which is an RC filter, is formed by the resistor _RL and the capacitor _CF. The power supply circuit 10 also includes elements not shown in FIG. 1, but the elements will be described later, and the configuration shown in FIG. 1 will be described first.

An input voltage Vin is supplied to the source of the output transistor M1. A drain of the output transistor M1 is connected to the node ND1. Although the drain of the output transistor M1 is directly connected to the node ND1 in FIG. 1, a resistor may be inserted between the drain of the output transistor M1 and the node ND1 (details will be described later).

Filter circuit FIL smoothes the voltage at node ND1 and generates the smoothed voltage as output voltage Vout (stabilized voltage). An output voltage Vout is developed at node ND2. Specifically, the node ND1 is connected to one end of the resistor _RF , and the other end of the resistor _RF and one end of the capacitor _CF are connected at a node ND2. The other end of capacitor _CF is connected to ground. Therefore, the voltage between both terminals of the capacitor _CF (that is, the charged voltage of the capacitor _CF ) becomes the output voltage Vout as the stabilized voltage.

A feedback circuit composed of feedback resistors R1 and R2 is provided between the node ND1 and the ground, and generates a feedback voltage Vfb corresponding to the voltage of the node ND1. Specifically, one end of the feedback resistor R1 is connected to the node ND1, and the other end of the feedback resistor R1 is grounded via the feedback resistor R2. A feedback voltage Vfb is developed at the connection node between the feedback resistors R1 and R2. Feedback voltage Vfb is transmitted to control circuit 11 . When the discharge current of the capacitor _CF is sufficiently small and the power supply circuit 10 is in a stable state, the voltage of the node ND1 and the output voltage Vout are substantially equal, so it is understood that the feedback voltage Vfb is a voltage proportional to the output voltage Vout. be able to.

The control circuit 11 is driven based on the input voltage Vin, and controls the gate voltage of the output transistor M1 so that the feedback voltage Vfb matches the predetermined reference voltage Vref. As a result, a voltage determined by the ratio of the resistance values of the feedback resistors R1 and R2 and the reference voltage Vref is set as the target voltage Vtg. The on-resistance value of the output transistor M1 is continuously controlled so that the voltage of ND1 matches the target voltage Vtg. The target voltage Vtg is represented by "Vtg=Vref×(R1+R2)/R2".

The control circuit 11 includes an amplifier 12, which is an operational amplifier, and a reference voltage source 13 that generates a reference voltage Vref. The reference voltage Vref has a predetermined positive DC voltage value (eg 0.5V). A reference voltage Vref is input to the inverting input terminal of the amplifier 12, a feedback voltage Vfb is input to the non-inverting input terminal of the amplifier 12, and the output terminal of the amplifier 12 is connected to the gate of the output transistor M1. Therefore, the amplifier 12 controls the gate voltage of the output transistor M1 so that the feedback voltage Vfb matches the predetermined reference voltage Vref.

The voltage output from the output terminal of the amplifier 12 is hereinafter referred to as a control voltage Vcnt. Using the term “control voltage Vcnt” can also be expressed as follows. Based on the feedback voltage Vfb and a predetermined reference voltage Vref, the control circuit 11 generates a control voltage Vcnt for matching the feedback voltage Vfb with a predetermined reference voltage Vref, and supplies the control voltage Vcnt to the gate of the output transistor M1. to control the state of the output transistor M1. The power supply voltage on the negative side of the control circuit 11 is 0V.

Since the power supply circuit 10 includes the filter circuit FIL using an RC filter, it has excellent ripple removal characteristics. The ripple elimination characteristic here is a characteristic for eliminating minute noise superimposed on the output voltage Vout due to the operation of the power supply circuit 10, and includes the power supply voltage fluctuation elimination ratio.

Although good ripple removal characteristics can be achieved, the start-up speed of the power supply circuit 10 tends to be slow due to the provision of the filter circuit FIL. That is, when the power supply circuit 10 is started, it may take a long time for the output voltage Vout to rise to the target voltage Vtg. Although not shown in FIG. 1, the power supply circuit 10 is provided with a circuit for increasing the startup speed.

Among the following examples EX1_1 to EX1_3 belonging to the first embodiment, specific examples of circuits for increasing the start-up speed will be described. The matters described above in the first embodiment are applied to the following examples EX1_1 to EX1_3 unless otherwise stated and there is no contradiction. The description in each example may be given priority. In addition, as long as there is no contradiction, the matter described in any one of the examples EX1_1 to EX1_3 can be applied to any other example (that is, any two or more examples among the plurality of examples) It is also possible to combine examples).

[Example EX1_1]
Example EX1_1 will be described. FIG. 2 is a circuit diagram of a power supply circuit 10A according to Example EX1_1. A power supply circuit 10A in FIG. 2 is an example of the power supply circuit 10. As shown in FIG. The power supply circuit 10A of FIG. 2 has a configuration in which a charging transistor M2 is added to the power supply circuit 10 of FIG. 1. Except for the addition, the power supply circuit 10A of FIG. is. Therefore, in Example EX1_1, only the configuration and operation related to the addition of the charging transistor M2 will be described below.

The charging transistor M2 is a P-channel MOSFET. The source of the charging transistor M2 is connected to the node ND1, and the drain of the charging transistor M2 is connected to the node ND2. A gate of the charging transistor M2 is connected to the output terminal of the amplifier 12 . Therefore, the control voltage Vcnt is commonly applied to the gates of the output transistor M1 and the charging transistor M2, and the state (on/off state) of the charging transistor M2 is controlled according to the control voltage Vcnt, similarly to the output transistor M1. will be

As shown in FIG. 3, it is assumed that the input voltage Vin gradually increases from 0V to 4.0V. Also, for concreteness of explanation, the target voltage Vtg is assumed to be 2.8V. Further, it is assumed that the threshold voltage Vth[M1] of the output transistor M1 and the threshold voltage Vth[M2] of the charging transistor M2 are both "-0.7V" (see FIG. 4).

When the gate potential of the output transistor M1 is lower than the source potential and the absolute value of the gate-source voltage of the output transistor M1 is equal to or greater than the voltage value |Vth[M1]|, the output transistor M1 is turned on; , the output transistor M1 is turned off. Similarly, when the gate potential of the charging transistor M2 is lower than the source potential and the absolute value of the voltage between the gate and the source of the charging transistor M2 is the voltage value |Vth[M2]| or more, the charging transistor M2 is turned on. state, otherwise the charging transistor M2 is turned off. Voltage values |Vth[M1]| and |Vth[M2]| represent absolute values of threshold voltages Vth[M1] and Vth[M2], respectively. When the output transistor M1 is in the ON state, the ON resistance value of the output transistor M1 decreases as the absolute value of the voltage between the gate and the source of the output transistor M1 increases. The same applies to the charging transistor M2.

FIG. 4 is a diagram showing behavior of the power supply circuit 10A when the input voltage Vin is 2.0V. The control circuit 11 is configured so that it can be driven when the input voltage Vin is equal to or higher than a predetermined starting voltage lower than 2.0V. That is, the control circuit 11 can generate and output the control voltage Vcnt for matching the feedback voltage Vfb with the predetermined reference voltage Vref when the input voltage Vin is equal to or higher than the starting voltage.

Amplifier 12 operates to lower control voltage Vcnt as the voltage at node ND1 is lower. Therefore, when the input voltage Vin is sufficiently lower than the target voltage Vtg after the control circuit 11 is activated, the control voltage Vcnt matches the lowest voltage that the amplifier 12 can output. The lowest voltage that the amplifier 12 can output substantially matches the negative power supply voltage of the amplifier 12 and is approximately 0V. When the lowest voltage that the amplifier 12 can output becomes the control voltage Vcnt, the output transistor M1 is in the ON state and the ON resistance value of the output transistor M1 is minimized. called.

As shown in FIG. 4, when the input voltage Vin is 2.0 V, the control voltage Vcnt is the lowest voltage that the amplifier 12 can output, and the output transistor M1 is fully on. Considering that the on-resistance value of the output transistor M1 at this time is sufficiently small, the voltage of the node ND1 is also 2.0 V if the on-resistance value is ignored. Then, the charging transistor M2 is also turned on, so that the current from the terminal to which the input voltage Vin is applied through the output transistor M1 flows to the capacitor _CF through the charging transistor M2 without passing through the resistor _RF . current and serves to charge the capacitor _CF.

FIG. 5 shows the behavior of the power supply circuit 10A when the input voltage Vin is 4.0V and the output voltage Vout is stabilized at the target voltage Vtg (here, 2.8V). In a stable state in which the input voltage Vin is 4.0 V, the amplifier 12 adjusts the voltage at the node ND1 to match the target voltage Vtg (in other words, the output voltage Vout reaches the target voltage Vtg) based on the feedback voltage Vfb. ), the control voltage Vcnt is approximately (Vin−|Vth[M1]|), ie, approximately 3.3 V, and the voltages at nodes ND1 and ND2 are approximately 2.8V. Then, since a reverse bias is applied to the charging transistor M2, the charging transistor M2 is turned off. Therefore, when the capacitor _CF is charged while the input voltage Vin is 4.0 V, the charging current flows through the resistor _RF without passing through the charging transistor M2.

Thus, in a predetermined first state (for example, the state of "Vin=2.0 V" in FIG. 4) in which the input voltage Vin is lower than the target voltage Vtg, the control circuit 11 controls the output transistor M1 and the charging voltage based on the feedback voltage Vfb. A voltage (for example, the lowest voltage that the amplifier 12 can output) that turns on both the control transistors M2 is generated as the control voltage Vcnt. On the other hand, in a predetermined second state where the input voltage Vin exceeds the target voltage Vtg (for example, the state of "Vin=4.0 V" in FIG. 5), the control circuit 11 turns the output transistor M1 on based on the feedback voltage Vfb. and a voltage (for example, 3.3 V) for turning off the charging transistor M2 is generated as the control voltage Vcnt.

When the difference between the voltages Vin and Vtg is very small, the charging transistor M2 behaves as an analog device and is in an intermediate state that can be said to be an on state or an off state. Therefore, the predetermined first state can be understood to refer to a state in which the input voltage Vin is lower than the target voltage Vtg and the difference between the voltages Vin and Vtg is equal to or greater than a predetermined voltage value (eg, 0.5 V). Similarly, the predetermined second state is understood to refer to a state in which the input voltage Vin exceeds the target voltage Vtg and the difference between the voltages Vin and Vtg is equal to or greater than a predetermined voltage value (eg, 0.5 V). good The control voltage Vcnt in the predetermined first state may be interpreted as a voltage for bringing the output transistor M1 into the full-on state.

According to the embodiment EX1_1, when the power supply circuit 10A is started (when the input voltage Vin rises), the capacitor _CF is charged via the charging transistor M2 without the resistor _RF , so that the output voltage Vout can be rapidly increased. stands up. After the input voltage Vin exceeds the target voltage Vtg, the charging transistor M2 is fixed in the off state and the filter circuit FIL including the resistor _RF functions effectively. Therefore, it is possible to increase the start-up speed while maintaining the good ripple removal characteristics of the filter circuit FIL.

In the power supply circuit 10A, depending on the rate of rise of the input voltage Vin, the response speed of the amplifier 12, etc., there is almost no opportunity to charge the capacitor _CF via the charging transistor M2, and the charging transistor M2 is turned off. It is also possible to become Therefore, when the circuit that detects the change in the input voltage Vin detects that the input voltage Vin starts to rise from 0 V, the control voltage Vcnt is maintained for a certain period of time (for example, 500 microseconds) regardless of the feedback voltage Vfb. It is also possible to include in the control circuit 11 a circuit that keeps V at or near 0V.

[Example EX1_2]
Example EX1_2 will be described. FIG. 6 is a circuit diagram of a power supply circuit 10B according to Example EX1_2. A power supply circuit 10B in FIG. 6 is an example of the power supply circuit 10 . The power supply circuit 10B of FIG. 6 has a configuration in which a charging transistor M3 and an insertion resistor R3 are added to the power supply circuit 10 of FIG. It is the same as 10. Therefore, in Example EX1_2, only the configuration and operation related to the addition of the charging transistor M3 and the insertion resistor R3 will be described below.

The charging transistor M3 is an N-channel MOSFET. The drain of the charging transistor M3 is connected to the node ND1, and the source of the charging transistor M3 is connected to the node ND2. In the power supply circuit 10B, an insertion resistor R3 is provided between the drain of the output transistor M1 and the node ND1. That is, one end of the insertion resistance R3 is connected to the drain of the output transistor M1, and the other end of the insertion resistance R3 is connected to the node ND1. The insertion resistor R3 is provided to turn on the charging transistor M3 when the power supply circuit 10B is activated. The current flowing through the insertion resistor R3 is represented by the symbol " _IR3 ", and the current flowing through the resistor _RF is represented by the symbol " _IRF ".

The operation of the power supply circuit 10B at startup will be described with reference to FIG. In FIG. 7, it is assumed that the input voltage Vin sharply rises from 0V to 4.0V at timing t1. It is also assumed that the target voltage Vtg is 2.8V. The control circuit 11 is activated as the input voltage Vin rises. Since the output voltage Vout and the feedback voltage Vfb are 0 V immediately after the control circuit 11 is started, the amplifier 12 sets the control circuit Vcnt to the lowest voltage that the amplifier 12 can output. As a result, the output transistor M1 is fully turned on.

In the ON state of the output transistor M1 including the full ON state, a charging current is supplied to the capacitor _CF via the output transistor M1 based on the input voltage Vin and the insertion resistor R3. When the input voltage Vin is 4.0 V, in the process in which the output voltage Vout rises from 0 V toward the target voltage Vtg, the voltage drop across the insertion resistor R3 reaches the threshold voltage Vth [M3] ( For example, 0.7 V) or higher, and the charging transistor M3 is turned on. Therefore, the charging current is supplied to the capacitor _CF via the charging transistor M3 rather than the resistor _RF . Between timings t1 and t2 in FIG. 4 is a section in which the charging transistor M3 is turned on due to a voltage drop across the insertion resistor _R3 . to the capacitor _CF.

When the output voltage Vout reaches the target voltage Vtg at timing t2, the amplifier 12 changes the control voltage Vcnt upward based on the feedback voltage Vfb. to the off state. Thereafter, when the output voltage Vout drops below the target voltage Vtg due to the decrease in the accumulated electric charge of the capacitor _CF , the charging current of the capacitor _CF is supplied via the resistor _RF . In FIG. 7, as an example, it is assumed that the load (not shown) connected to the node ND2 continuously draws the stored charge of the capacitor _CF by a very small amount of current.

As described above, the charging transistor M3 switches from the ON state to the OFF state when the output voltage Vout reaches the target voltage Vtg. 2.8V), the charging transistor M3 may be switched off. For example, if the input voltage Vin after timing t1 is 3.0V, and the threshold voltage Vth[M3] of the charging transistor M3 is 0.7V, the output voltage Vout reaches about 2.3V. The charging transistor M3 is switched off, and henceforth the charging current of the capacitor _CF will be supplied via the resistor _RF .

Thus, in the power supply circuit 10B, the charging transistor M3 whose state (on/off state) is controlled based on the voltage drop of the insertion resistor R3 is provided between the nodes ND1 and ND2. Then, when the voltage at the drain of the output transistor M1 seen from the potential of the node ND2 is equal to or higher than the threshold voltage Vth[M3] of the charging transistor M3, the charging transistor M3 is turned on. capacitor _CF is charged via .

In FIG. 7, for convenience of explanation, it is assumed that the input voltage Vin sharply rises from 0 V to 4 V at the timing t1. A charging current is supplied to the capacitor _CF through the charging transistor M3 in a section where the voltage drop across the resistor R3 is equal to or higher than the threshold voltage Vth [M3].

According to the embodiment EX1_2, when the power supply circuit 10B is started, the capacitor _CF is charged through the charging transistor M3 and not through the resistor _RF , so that the output voltage Vout quickly rises. After the output voltage Vout reaches the target voltage Vtg, or after the output voltage Vout reaches near the target voltage Vtg, the charging transistor M3 is turned off and the filter circuit FIL including the resistor _RF is turned off. Works effectively. Therefore, it is possible to increase the start-up speed while maintaining the good ripple removal characteristics of the filter circuit FIL.

Although the back gate of the charging transistor M3 is connected to the source in FIG. 6, the back gate of the charging transistor M3 may be connected to the ground instead of the source as shown in FIG. This makes it possible to increase the threshold voltage Vth[M3] of the charging transistor M3 based on the substrate bias effect. In addition, since the parasitic diode of the charging transistor M3 is not generated, it is possible to suppress the occurrence of reverse current flowing from the node ND2 to the node ND1.

[Example EX1_3]
Example EX1_3 will be described. FIG. 9 is a circuit diagram of a power supply circuit 10C according to Example EX1_3. A power supply circuit 10</b>C in FIG. 9 is an example of the power supply circuit 10 . The power supply circuit 10C has a configuration in which the configurations of the examples EX1_1 and EX1_2 are combined. That is, the power supply circuit 10C of FIG. 9 has a configuration in which charging transistors M2 and M3 and an insertion resistor R3 are added to the power supply circuit 10 of FIG. 1 is the same as the power supply circuit 10 of FIG.

The connection relationship between the charging transistor M2 and other circuit elements, and the configuration and operation of the charging transistor M2 are as described in Example EX1_1. The connection relationship between the charging transistor M3 and the insertion resistor R3 and other circuit elements, and the configuration and operation of the charging transistor M3 are as described in Example EX1_2. According to Example EX1_3, the action/effect shown in Example EX1_1 and the action/effect shown in Example EX1_2 can be obtained.

<<Second Embodiment>>
A second embodiment of the present invention will be described. The second embodiment is based on the first embodiment, and as long as there is no contradiction, the description of the first embodiment is also applied to the second embodiment regarding matters not specifically described in the second embodiment. be. In interpreting the description of the second embodiment, the description of the second embodiment may take precedence over any contradictory matters between the first and second embodiments.

The second embodiment includes the following examples EX2_1 to EX2_4. As long as there is no contradiction, the matter described in any of Examples EX2_1 to EX2_4 can also be applied to any other example (that is, any two or more examples among a plurality of examples) can also be combined).

[Example EX2_1]
Example EX2_1 will be described. A power supply including the power supply circuit 10 shown in the first embodiment may be configured, and the power supply circuit 10 can be used as an internal power supply or a reference voltage source in the power supply.

FIG. 10 shows the configuration of a power supply device 100 according to Example EX2_1. The power supply device 100 includes an input terminal TM1, an output terminal TM2, a ground terminal TM3, a power supply circuit 10, and an output circuit 20. As the power supply circuit 10 in the power supply device 100, any one of the power supply circuits 10A, 10B, and 10C shown in the first embodiment can be used. The input voltage Vin described above is applied to the input terminal TM1. A ground terminal TM3 is connected to the ground. The output voltage V _OUT of the power supply device 100 is applied to the output terminal TM2.

The output circuit 20 comprises an amplifier 21, which is an operational amplifier, and generates a final output voltage _VOUT based on the output voltage Vout of the power supply circuit 10. FIG. In the amplifier 21, the power supply voltage on the positive side is the input voltage Vin, and the power supply voltage on the negative side is 0V. The amplifier 21 is used as a voltage follower in the output circuit 20, and a voltage obtained by performing impedance conversion on the output voltage Vout of the power supply circuit 10 is output from the output terminal TM2 as the output voltage _VOUT . That is, the non-inverting input terminal of the amplifier 21 is connected to the node ND2 (see FIG. 4 etc. as appropriate), and the inverting input terminal and output terminal of the amplifier 21 are commonly connected to the output terminal TM2. As a result, the output voltage VOUT having the same voltage value as the output voltage _Vout is output from the output terminal TM2 with low impedance.

[Example EX2_2]
Example EX2_2 will be described. The output voltage Vout of the power supply circuit 10 (10A, 10B or 10C) can be supplied to any load device, and the output voltage _VOUT of the power supply device 100 can be supplied to any load device. In the following, consider supplying the output voltage V _OUT of power supply 100 to an arbitrary load device.

Any electrical device including the power supply device 100 and the load device may be configured. The load device is driven based on the output voltage V _OUT of power supply 100 . The electric device may be a device mounted on a vehicle such as an automobile (that is, a vehicle-mounted device), or may be an industrial device, an office device, a home appliance, a portable device including an information terminal, or the like.

FIG. 11 shows a schematic external view of a smart phone 200 as an example of an electric device including the power supply device 100 and a load device. The smart phone 200 is a type of mobile phone and a type of information terminal. In the smart phone 200, the load device driven based on the output voltage V _OUT of the power supply device 100 may be any load (processor, memory, liquid crystal driver, communication IC, etc.) driven by DC power.

[Example EX2_3]
Example EX2_3 will be described. The power supply device 100 may be formed in the form of a power supply IC. At this time, the power supply IC as the power supply device 100 includes a semiconductor chip formed with a semiconductor integrated circuit that constitutes the power supply device 100, a housing (package) that houses the semiconductor chip, and a package that is attached to the housing and extends from the housing. It is an electronic component (semiconductor device) having a plurality of exposed external terminals, and is formed by enclosing a semiconductor chip in a housing made of resin. Terminals TM1 to TM3 in FIG. 10 are included in the plurality of external terminals.

[Example EX2_4]
Example EX2_4 will be described. Each of the transistors described above may be of any type without departing from the scope of the discussion. For example, a P-channel MOSFET can be replaced with an N-channel MOSFET, or an N-channel MOSFET can be replaced with a P-channel MOSFET, without impairing the gist of the above. It is also possible to replace the MOSFET with a PNP-type bipolar transistor and replace the N-channel MOSFET with an NPN-type bipolar transistor. A modification is also possible in which the MOSFET is replaced with a junction FET or IGBT.

Any transistor has a first electrode, a second electrode and a control electrode. In a FET, one of the first and second electrodes is the drain and the other is the source, and the control electrode is the gate. In an IGBT, one of the first and second electrodes is the collector and the other is the emitter, and the control electrode is the gate. In a bipolar transistor not belonging to an IGBT, one of the first and second electrodes is the collector and the other is the emitter and the control electrode is the base.

The embodiments of the present invention can be appropriately modified in various ways within the scope of the technical idea indicated in the scope of claims. The above embodiments are merely examples of the embodiments of the present invention, and the meanings of the terms of the present invention and each constituent element are not limited to those described in the above embodiments. The specific numerical values given in the above description are merely examples and can of course be changed to various numerical values.

10, 10A to 10C power supply circuit 11 control circuit 12 amplifier 13 reference voltage source 20 output circuit 100 power supply device M1 output transistor M2, M3 charging transistor R1, R2 feedback resistor R3 insertion resistor _RF filter resistor C capacitor for _F filter

Claims (12)

A power supply circuit that generates a stabilized voltage from an input voltage,
an output transistor having a first electrode for receiving the input voltage, a second electrode, and a control electrode;
a first node directly connected to the second electrode of the output transistor or connected via an insertion resistor;
a control circuit that controls the state of the output transistor by supplying a control voltage based on a feedback voltage corresponding to the voltage of the first node to a control electrode of the output transistor;
a filter circuit having a filter resistor and a filter capacitor and smoothing the voltage of the first node to generate the stabilized voltage at the second node;
a charging transistor provided between the first node and the second node, the state of which is controlled based on the control voltage;
When the charging transistor is turned on, the filtering capacitor is charged through the charging transistor ,
The output transistor and the charging transistor are configured as P-channel MOSFETs,
the first electrode, the second electrode and the control electrode of the output transistor are respectively the source, the drain and the gate of the output transistor;
a source and a drain of the charging transistor are connected to the first node and the second node, respectively;
The control voltage is commonly applied to each gate of the output transistor and the charging transistor.
, power circuit. A power supply circuit that generates a stabilized voltage from an input voltage,
an output transistor having a first electrode for receiving the input voltage, a second electrode, and a control electrode;
a first node directly connected to the second electrode of the output transistor or connected via an insertion resistor;
a control circuit that controls the state of the output transistor by supplying a control voltage based on a feedback voltage corresponding to the voltage of the first node to a control electrode of the output transistor;
a filter circuit having a filter resistor and a filter capacitor and smoothing the voltage of the first node to generate the stabilized voltage at the second node;
a charging transistor provided between the first node and the second node, the state of which is controlled based on the control voltage;
When the charging transistor is turned on, the filtering capacitor is charged through the charging transistor,
the first node is connected to the second electrode of the output transistor via the insertion resistor;
a second charging transistor provided between the first node and the second node, the state of which is controlled based on the voltage drop across the insertion resistor;
, power circuit. When the voltage at the second electrode of the output transistor seen from the potential of the second node is equal to or higher than the threshold voltage of the second charging transistor, the second charging transistor is turned on and the second charging transistor is turned on. 2 the filter capacitor is charged via a charging transistor
3. The power supply circuit of claim 2. The second charging transistor is configured as an N-channel MOSFET,
the drain and source of the second charging transistor are connected to the first node and the second node, respectively;
A gate of the second charging transistor is connected to a second electrode of the output transistor
4. The power supply circuit according to claim 2 or 3 . The output transistor and the charging transistor are configured as P-channel MOSFETs,
the first electrode, the second electrode and the control electrode of the output transistor are respectively the source, the drain and the gate of the output transistor;
a source and a drain of the charging transistor are connected to the first node and the second node, respectively;
The control voltage is commonly applied to each gate of the output transistor and the charging transistor.
The power supply circuit according to any one of claims 2 to 4 . The power supply circuit is a linear regulator that controls the output transistor so that the stabilized voltage matches a predetermined target voltage,
The control circuit generates, as the control voltage, a voltage that turns on both the output transistor and the charging transistor based on the feedback voltage in a predetermined first state in which the input voltage is lower than the target voltage, In a predetermined second state in which the input voltage exceeds the target voltage, a voltage for turning on the output transistor and turning off the charging transistor based on the feedback voltage is generated as the control voltage.
The power supply circuit according to any one of claims 1 to 5 . The filter resistor is provided between the first node and the second node, and the filter resistor and the filter capacitor are connected to each other at the second node.
The power supply circuit according to any one of claims 1 to 6 . A power supply circuit that generates a stabilized voltage from an input voltage,
an output transistor having a first electrode for receiving the input voltage, a second electrode, and a control electrode;
a first node connected to the second electrode of the output transistor via an insertion resistor;
a control circuit that controls the state of the output transistor by supplying a control voltage based on a feedback voltage corresponding to the voltage of the first node to a control electrode of the output transistor;
a filter circuit having a filter resistor and a filter capacitor and smoothing the voltage of the first node to generate the stabilized voltage at the second node;
a charging transistor provided between the first node and the second node, the state of which is controlled based on the voltage drop across the insertion resistor;
When the charging transistor is turned on, the filtering capacitor is charged through the charging transistor.
, power circuit. When the voltage at the second electrode of the output transistor seen from the potential of the second node is equal to or higher than the threshold voltage of the charging transistor, the charging transistor is turned on, and the charging transistor is driven through the charging transistor. the filter capacitor is charged by
9. A power supply circuit according to claim 8. The charging transistor is configured as an N-channel MOSFET,
the drain and source of the charging transistor are connected to the first node and the second node, respectively;
A gate of the charging transistor is connected to a second electrode of the output transistor
10. The power supply circuit according to claim 8 or 9. The filter resistor is provided between the first node and the second node, and the filter resistor and the filter capacitor are connected to each other at the second node.
The power supply circuit according to any one of claims 8 to 10 . A power supply circuit according to any one of claims 1 to 11;
an output circuit that receives the stabilized voltage generated by the power supply circuit with a voltage follower and generates an output voltage.
, power supply.

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