Linear power supply circuit and vehicle

Abstract

To provide a linear power supply circuit capable of attaining both of low power consumption and an excellent load regulation characteristic.SOLUTION: A linear power supply circuit includes an error amplifier (A1) that outputs an error signal dependent on a difference between a feedback voltage based on an output voltage and a reference voltage, a first transistor (Q1) that is controlled with the error signal, a current mirror circuit (Q2 and Q3), a bias current source (IS1) that supplies a bias current by distributing into the transistor and current mirror circuit, a current amplifier (A2) that amplifies a current outputted from the current mirror circuit, and a compensation unit (Q4 to Q6, C1, and R1) that compensates for the bias current with a current dependent on the current outputted from the current amplifier.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The invention disclosed in this specification relates to a linear power supply circuit and a vehicle equipped with the linear power supply circuit. [Background technology]

[0002] Linear power supply circuits such as LDOs (low drop outs) are used as power supply means for various devices. Patent Document 1 can be cited as an example of prior art related to linear power supply circuits. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-71681 Summary of the Invention [Problem to be solved by the invention]

[0004] In a low-power linear power supply circuit, if the output capacitor is small or the load is heavy, the gain may not be large enough to ensure phase alignment. If the gain cannot be large enough, the load regulation characteristics of the linear power supply circuit will deteriorate. [Means for solving the problem]

[0005] The linear power supply circuit disclosed in this specification includes an error amplifier configured to output an error signal corresponding to the difference between a feedback voltage based on an output voltage and a reference voltage, a first transistor configured to be controlled by the error signal, a current mirror circuit, a bias current source configured to distribute and supply a bias current to the first transistor and the current mirror circuit, and a current amplifier configured to amplify a current output from the current mirror circuit. supplied to the current mirror circuit The bias current is controlled by a current corresponding to the current. In the area below a certain frequencyand a compensation unit configured to compensate.

[0006] The vehicle disclosed in this specification is equipped with the linear power supply circuit having the above configuration. [Effects of the Invention]

[0007] According to the invention disclosed in this specification, it is possible to achieve both low power consumption and good load regulation characteristics in a linear power supply circuit. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram showing an example of the configuration of a linear power supply circuit according to an embodiment. [Figure 2] FIG. 2 is a diagram illustrating an example of the configuration of the current amplifier. [Figure 3] FIG. 3 is a diagram showing the gain characteristics of the transfer function of the portion of the linear power supply circuit excluding the compensation unit, the output capacitor, and the load. [Figure 4] FIG. 4 is a diagram showing other gain characteristics of the transfer function of the portion of the linear power supply circuit excluding the compensation unit, the output capacitor, and the load. [Figure 5] FIG. 5 is a diagram showing still another gain characteristic of the transfer function of the portion of the linear power supply circuit excluding the compensation unit, the output capacitor, and the load. [Figure 6] FIG. 6 is a diagram showing still another gain characteristic of the transfer function of the linear power supply circuit, the output capacitor, and the load. [Figure 7] FIG. 7 is an external view of the vehicle. DETAILED DESCRIPTION OF THE INVENTION

[0009] In this specification, the reference voltage means a voltage that is constant under ideal conditions, but in reality it is a voltage that may fluctuate slightly due to temperature changes and the like.

[0010] In this specification, a constant current means a current that is constant under ideal conditions, but in reality it is a current that may fluctuate slightly due to temperature changes and the like.

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

[0012] Fig. 1 is a diagram showing an example of the configuration of a linear power supply circuit according to an embodiment. The linear power supply circuit 1 shown in Fig. 1 includes an error amplifier A1, first to sixth transistors Q1 to Q6, a bias current source IS1, a current amplifier A2, a capacitor C1, a resistor R1, a bypass capacitor CF, and a reference voltage source VS1. An output capacitor Co and a load RL are externally connected to the linear power supply circuit 1.

[0013] The linear power supply circuit 1 converts an input voltage VIN into an output voltage Vo, and supplies the output voltage Vo to an output capacitor Co and a load RL.

[0014] A feedback voltage based on the output voltage Vo is supplied to the non-inverting input terminal of the error amplifier A1. A reference voltage VREF output from a reference voltage source VS1 is supplied to the inverting input terminal of the error amplifier A1. The error amplifier A1 outputs an error signal corresponding to the difference between the feedback voltage and the reference voltage VREF. In the configuration example shown in Figure 1, the feedback voltage is the same as the output voltage Vo. However, unlike the configuration example shown in Figure 1, the feedback voltage may be a divided voltage of the output voltage Vo.

[0015] The gain of the error amplifier A1 is preferably 1.

[0016] A feedback voltage is supplied to a first terminal of the bypass capacitor CF, and a second terminal of the bypass capacitor CF is connected to the output terminal of the error amplifier A1.

[0017] The first transistor Q1 is controlled by an error signal output from an error amplifier A1. In the configuration example shown in Figure 1, an N-channel MOSFET is used as the first transistor Q1.

[0018] An input voltage VIN is supplied to a first terminal of the bias current source IS1. A second terminal of the bias current source IS1 is connected to the drain of the first transistor Q1. A bias current IBias is output from the second terminal of the bias current source IS1. The bias current IBias is a constant current. The source of the first transistor Q1 is connected to the ground potential. By reducing the bias current IBias, the power consumption of the linear power supply circuit 1 can be reduced.

[0019] The bias current IBias is distributed and supplied to the first transistor Q1 and a current sink-type current mirror circuit formed by the second transistor Q2 and the third transistor Q3. In the configuration example shown in Figure 1, an N-channel MOSFET is used as the second transistor Q2, and an N-channel MOSFET is used as the third transistor Q3. The gate and drain of the second transistor Q2 and the gate of the third transistor Q3 are connected to the drain of the first transistor Q1. The sources of the second transistor Q2 and the third transistor Q3 are connected to the ground potential.

[0020] The current amplifier A2 amplifies the current output from a current sink type current mirror circuit formed by a second transistor Q2 and a third transistor Q3. The current amplifier A2 is driven by a constant voltage Vc. The current output from the current amplifier A2 is supplied to an output capacitor Co and a load RL.

[0021] Fig. 2 is a diagram showing an example of the configuration of the current amplifier A2. The current amplifier A2 of the example configuration shown in Fig. 2 includes a plurality of current source type current mirror circuits and a plurality of current sink type current mirror circuits. The current source type current mirror circuits and the current sink type current mirror circuits are alternately arranged from the input to the output of the current amplifier A2.

[0022] 3 is a diagram showing the gain characteristics of the transfer function of the portion of the linear power supply circuit 1 excluding the compensation unit, the output capacitor Co, and the load RL. The compensation unit is composed of fourth to sixth transistors, a capacitor C1, and a resistor R1. Details of the compensation unit will be described later.

[0023] The frequency FP1 of the first pole is determined by the capacitance value of the output capacitor Co and the resistance value of the load RL. The smaller the capacitance value of the output capacitor Co, the higher the frequency FP1 of the first pole becomes and the closer it is to the frequency FP2 of the second pole. Also, the larger the resistance value of the load RL, the higher the frequency FP1 of the first pole becomes and the closer it is to the frequency FP2 of the second pole.

[0024] The frequency FP2 of the second pole is determined by the specific circuit configuration of the current amplifier A2. Since there are various restrictions on the specific circuit configuration of the current amplifier A2, there is an upper limit to the frequency FP2 of the second pole.

[0025] Moreover, the slope of the gain from the frequency FP1 of the first pole to the frequency FP2 of the second pole is theoretically constant.

[0026] Therefore, when the capacitance value of the output capacitor Co is small, or the resistance value of the load RL is large, or both, the frequency FP1 of the first pole approaches the frequency FP2 of the second pole, which may result in the frequency FP2 of the second pole becoming lower than the zero-cross frequency ZC, as shown in Figure 4. Note that the thick dotted line in Figure 4 indicates the gain characteristic shown in Figure 3.

[0027] To ensure stable operation of the linear power supply circuit 1 while maintaining the phase, the frequency FP2 of the second pole must be higher than the zero-cross frequency ZC. Therefore, when the capacitance of the output capacitor Co is small, the resistance of the load RL is large, or both, it is necessary to lower the gain as shown in Figure 5 to raise the frequency FP2 of the second pole above the zero-cross frequency ZC. However, lowering the gain as shown in Figure 5 results in a deterioration of the load regulation characteristics. The thick dotted line in Figure 5 indicates the gain characteristics shown in Figure 3.

[0028] The linear power supply circuit 1 has a compensation section that compensates for the bias current IBias with a current corresponding to the current output from the current amplifier A2, thereby improving the load regulation characteristics.

[0029] 1, the compensation unit includes fourth to sixth transistors Q4 to Q6, a capacitor C1, and a resistor R1. The compensation unit is driven by a constant voltage Vc. In the configuration example shown in FIG. 1, an N-channel MOSFET is used as the fourth transistor Q4, a P-channel MOSFET is used as the fifth transistor Q5, and a P-channel MOSFET is used as the sixth transistor Q6.

[0030] The gate of the fourth transistor Q4 is commonly connected to the gates of the second transistor Q2 and the third transistor Q3. The source of the fourth transistor Q4 is connected to ground. Therefore, the drain current of the fourth transistor Q4 depends on the drain current of the second transistor Q2. That is, the drain current of the fourth transistor Q4 is a current that corresponds to the drain current of the second transistor Q2. By providing the fourth transistor Q4, the current is returned to the bias current source IS1 side from a position close to the bias current source IS1, so that the compensation section can be configured compactly.

[0031] The drain and gate of the fifth transistor Q5 are connected to the drain of the fourth transistor Q4. A constant voltage Vc is applied to the source of the fifth transistor Q5, the first terminal of the capacitor C1, and the source of the sixth transistor Q6. The drain and gate of the fifth transistor Q5 are connected to the second terminal of the capacitor C1 and the gate of the sixth transistor Q6 via a resistor R1. The drain of the sixth transistor Q6 is connected to the drain of the first transistor.

[0032] In a frequency range below a predetermined frequency determined by the time constant of a CR circuit formed by capacitor C1 and resistor R1, the fifth transistor Q5 and the sixth transistor Q6 form a current source type current mirror circuit. Therefore, in a frequency range below the predetermined frequency, the compensator compensates for the bias current IBias using the drain current of the sixth transistor Q6. On the other hand, in a frequency range above the predetermined frequency, the sixth transistor Q6 is turned off by capacitor C1, so the compensator does not compensate for the bias current IBias.

[0033] FIG. 6 is a diagram showing the gain characteristics of the transfer function of the linear power supply circuit 1, the output capacitor Co, and the load RL.

[0034] FIG. 6 shows a gain characteristic T1 of the transfer function of the portion of the linear power supply circuit 1 excluding the compensation section, the output capacitor Co, and the load RL, and a gain characteristic T2 of the transfer function of the compensation section of the linear power supply circuit 1.

[0035] In the gain path, the compensation section of the linear power supply circuit 1 is added in parallel to the portion of the linear power supply circuit 1 excluding the compensation section. As a result, the gain characteristics of the transfer function of the linear power supply circuit 1, output capacitor Co, and load RL form an envelope (thick dotted line in Figure 6) in which the higher gain of the gain characteristics T1 and T2 is selected.

[0036] In the region below a certain frequency, the bias current IBias is compensated for by the compensation section, resulting in a high gain. This improves the load regulation characteristics.

[0037] 7 is an external view of a vehicle X. The vehicle X of this configuration example is equipped with various electronic devices X11 to X18 that operate by receiving a supply of voltage output from a battery (not shown). Note that the installation positions of the electronic devices X11 to X18 in this figure may differ from the actual positions for convenience of illustration.

[0038] The electronic device X11 is an engine control unit that performs engine-related controls (injection control, electronic throttle control, idling control, oxygen sensor heater control, auto-cruise control, etc.).

[0039] The electronic device X12 is a lamp control unit that controls the turning on and off of HID (high intensity discharged lamp) and DRL (daytime running lamp).

[0040] The electronic device X13 is a transmission control unit that controls transmission-related functions.

[0041] The electronic device X14 is a braking unit that performs control related to the movement of the vehicle X (ABS (anti-lock brake system) control, EPS (electric power steering) control, electronic suspension control, etc.).

[0042] The electronic device X15 is a security control unit that controls the operation of door locks, burglar alarms, and other devices.

[0043] The electronic device X16 is an electronic device that is installed in the vehicle X at the time of shipment from the factory as a standard equipment or a manufacturer option, such as a wiper, an electric door mirror, a power window, a damper (shock absorber), an electric sunroof, and an electric seat.

[0044] The electronic device X17 is an electronic device that is optionally installed in the vehicle X as a user option, such as an in-vehicle A / V (audio / visual) device, a car navigation system, and an ETC (electronic toll collection system).

[0045] The electronic device X18 is an electronic device equipped with a high-voltage motor, such as an in-vehicle blower, oil pump, water pump, or battery cooling fan.

[0046] The linear power supply circuit described above can be incorporated into any of the electronic devices X11 to X18.

[0047] <Other> The above-described embodiments should be considered to be illustrative in all respects and not restrictive. The technical scope of the invention disclosed in this specification is indicated by the claims, not by the description of the above-described embodiments, and should be understood to include all modifications that fall within the meaning and scope equivalent to the claims.

[0048] For example, instead of the MOSFETs used in the above embodiments, bipolar transistors may be used.

[0049] The linear power supply circuit described above includes an error amplifier (A1) configured to output an error signal corresponding to the difference between a feedback voltage based on an output voltage and a reference voltage, a first transistor (Q1) configured to be controlled by the error signal, a current mirror circuit (Q2, Q3), a bias current source (IS1) configured to distribute and supply a bias current to the first transistor and the current mirror circuit, and a current amplifier unit (A2) configured to amplify a current output from the current mirror circuit. supplied to the current mirror circuit and a compensation section (Q4 to Q6, C1, R1) configured to compensate for the bias current with a current corresponding to the current (first configuration).

[0050] The linear power supply circuit having the first configuration can achieve both low power consumption and good load regulation characteristics by reducing the bias current.

[0051] In the linear power supply circuit having the first configuration, the compensation section may be configured to compensate for the bias current in a region equal to or lower than a predetermined frequency (second configuration).

[0052] The linear power supply circuit having the second configuration can improve the load regulation characteristics without the compensation section affecting the first pole frequency and the second pole frequency.

[0053] In the linear power supply circuit having the second configuration, the compensation section may have a configuration (third configuration) including a CR circuit made up of a capacitor (C1) and a resistor (R1).

[0054] In the linear power supply circuit having the third configuration, the frequency range in which the bias current is compensated can be adjusted by the time constant of the CR circuit.

[0055] In the linear power supply circuit of the third configuration, the compensation unit may be configured (fourth configuration) to include a fourth transistor (Q4) having a control terminal commonly connected to the control terminals of the second transistor (Q2) and the third transistor (Q3) that constitute the current mirror circuit.

[0056] The linear power supply circuit having the fourth configuration allows the compensation section to have a compact configuration.

[0057] In the linear power supply circuit of the fourth configuration, the compensation section may be configured (fifth configuration) to include a current source type current mirror circuit (Q5, Q6) configured to supply current to the connection node of the first transistor and the current mirror circuit and to the fourth transistor, respectively.

[0058] The linear power supply circuit having the fifth configuration can realize a compensation section with a simple configuration.

[0059] In the linear power supply circuit having the fifth configuration described above, the CR circuit may be configured (sixth configuration) to be provided between the control terminals of a fifth transistor (Q5) and a sixth transistor (Q6) that constitute the current mirror circuit.

[0060] The linear power supply circuit having the sixth configuration can realize a compensation section with a simple configuration.

[0061] In the linear power supply circuit having any of the first to sixth configurations, the gain of the error amplifier may be 1 (seventh configuration).

[0062] The linear power supply circuit having any of the above first to seventh configurations may also have a configuration (eighth configuration) in which a bypass capacitor is provided, and the bypass capacitor is configured so that the feedback voltage is supplied to a first terminal of the bypass capacitor and the output terminal of the error amplifier is connected to a second terminal of the bypass capacitor.

[0063] In the linear power supply circuit having any one of the first to eighth configurations, the current mirror circuit may be a current sink type current mirror circuit (ninth configuration).

[0064] The vehicle described above has a configuration (tenth configuration) that includes a linear power supply circuit having any one of the first to ninth configurations.

[0065] In the vehicle having the tenth configuration, both low power consumption and good load regulation characteristics can be achieved in the linear power supply circuit. [Explanation of symbols]

[0066] 1 Linear power supply circuit A1 Error amplifier A2 Current amplifier C1 capacitor CF Bypass capacitor Co Output Capacitor IS1 bias current source Q1~Q6 1st to 6th transistors R1 Resistor RL load VS1 Reference voltage source X vehicle X11~X18 Electronic equipment

Claims

1. an error amplifier configured to output an error signal corresponding to a difference between a feedback voltage based on the output voltage and a reference voltage; a first transistor configured to be controlled by the error signal; A current mirror circuit; a bias current source configured to distribute and supply a bias current to the first transistor and the current mirror circuit; a current amplifier configured to amplify the current output from the current mirror circuit; a compensation unit configured to compensate the bias current in a region equal to or lower than a predetermined frequency by a current corresponding to the current supplied to the current mirror circuit; A linear power supply circuit comprising:

2. 2. The linear power supply circuit according to claim 1, wherein the compensation section includes a CR circuit configured with a capacitor and a resistor.

3. 3. The linear power supply circuit according to claim 2, wherein the compensation section includes a fourth transistor having a control terminal commonly connected to the control terminals of the second and third transistors that constitute the current mirror circuit.

4. 4. The linear power supply circuit according to claim 3, wherein the compensation section includes a current source type current mirror circuit configured to supply current to a connection node between the first transistor and the current mirror circuit, and to the fourth transistor.

5. 5. The linear power supply circuit according to claim 4, wherein the CR circuit is provided between control terminals of a fifth transistor and a sixth transistor that constitute the current mirror circuit.

6. 6. The linear power supply circuit according to claim 1, wherein the gain of the error amplifier is 1.

7. A bypass capacitor is provided.

7. The linear power supply circuit according to claim 1, wherein the bypass capacitor is configured such that the feedback voltage is supplied to a first terminal of the bypass capacitor and the output terminal of the error amplifier is connected to a second terminal of the bypass capacitor.

8. 8. The linear power supply circuit according to claim 1, wherein the current mirror circuit is a current sink type current mirror circuit.

9. A vehicle comprising the linear power supply circuit according to any one of claims 1 to 8.

Images