JP2008269066A - Power circuit and power supply circuit system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power circuit and a power supply circuit system capable of preventing an output voltage from becoming out of control by the currents flowing into a power output line, while reducing increase in circuit scale. <P>SOLUTION: In a series regulator type power circuit 13, a diode 22 is connected between a power output terminal 10 and a base of a transistor 12 while using the power output terminal 10 side as an anode. When the output voltage VCL is increased beyond a target value by inflow of the current into the power output line 23 from the outside of the power circuit 13, an operational amplifier 3 reduces a base voltage of the transistor 12, and the diode 22 is biased forward. The current flowing into the power output line 23 flows to the ground via the diode 22 and the transistor in an output step of the operational amplifier 3. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a power supply circuit that controls an output voltage to a target value by controlling driving of a main transistor interposed between a power supply input line and a power supply output line, and a power supply circuit system including the power supply circuit.

  Some in-vehicle semiconductor integrated circuit devices are provided with a clamp circuit so that a battery voltage higher than its own operating power supply voltage can be directly applied to an input terminal. Among the clamp circuits, there is one in which a semiconductor element to be used is configured without increasing the withstand voltage and can be manufactured by a normal forming process (for example, see Patent Document 1). In this case, when performing a clamping operation, an intermediate voltage (voltage between the power supply voltage and the ground) is applied to a plurality of semiconductor switching elements constituting the circuit to control the conduction state of each element. Yes.

  However, when the intermediate voltage is lower than the battery voltage, current flows into the voltage output line of the intermediate voltage generation circuit that generates the intermediate voltage from the clamp circuit side, and the intermediate voltage generation circuit becomes unable to control the output voltage. There is. In order to solve this problem, an input interface circuit is proposed in which a voltage follower circuit having a high sink capability is provided between the clamp circuit and the intermediate voltage generation circuit, and current flowing into the intermediate voltage generation circuit side is sinked to the ground. (For example, refer to Patent Document 2).

  FIG. 3 illustrates the configuration of a microcomputer and its peripheral circuits when the input interface circuit is applied to a vehicle-mounted microcomputer (hereinafter referred to as a microcomputer). The microcomputer 1 in FIG. 3 includes a reference voltage generation circuit 2, operational amplifiers 3 and 4, a voltage detection circuit 5, a clamp circuit 6, power supply input terminals 7 and 8, a REF terminal 9, a power supply output terminal 10, and an input terminal 11. .

  Among these, the reference voltage generation circuit 2, the operational amplifier 3 and the voltage detection circuit 5, and the transistor 12 outside the microcomputer 1 constitute a power supply circuit 13. Outside the microcomputer 1, a capacitor C1 is connected between the power output terminal 10 and the ground (0 V). The input terminal 11 is connected to the battery power supply line via the resistor R1, and is connected to the ground via the switch S1. The parasitic diode and parasitic transistor in the clamp circuit 6 are indicated by broken lines in FIG.

According to the above configuration, when the switch S1 is turned off and the battery voltage + B is applied to the input terminal 11 via the resistor R1, the voltage at the input terminal 11 is clamped to approximately the power supply voltage VDD by the operation of the clamp circuit 6. Is done. At this time, a current flows from the battery power supply line to the power supply output line of the power supply circuit 13 via the clamp circuit 6, and this current is a transistor provided in the output stage of the operational amplifier 4 functioning as a voltage follower circuit (FIG. (Not shown) to the ground. As a result, a situation in which the output voltage cannot be controlled in the power supply circuit 13 can be prevented.
JP 2002-043924 A JP 2005-269515 A

  However, in the conventional configuration, the operational amplifier 4 (voltage follower circuit) needs to be provided in all the input terminals 11 to which the battery voltage + B may be applied in the microcomputer 1, and the number of target input terminals 11 There is a problem that the circuit scale increases in proportion to

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a power supply circuit and a power supply circuit capable of preventing a situation in which the output voltage cannot be controlled due to a current flowing into the power supply output line while suppressing an increase in circuit scale. To provide a system.

  According to the means of the first aspect, the amplifier circuit is connected between the power input line and the power output line based on the reference voltage corresponding to the target value of the output voltage and the detected voltage corresponding to the voltage of the power output line. A drive signal is output to the control terminal of the main transistor that is interposed between and the output voltage is controlled to a target value. Thus, when the output voltage is controlled to the target value, the diode connected with the power output line side as an anode between the power output line and the control terminal of the main transistor is reverse-biased, so that the above control operation is performed. Has no effect.

  On the other hand, when a current flows into the power supply output line from the outside of the power supply circuit, if the current is larger than the current supplied to the load, the output voltage exceeds the target value. When the voltage between the power supply output line and the control terminal of the main transistor becomes the forward voltage of the diode, the diode is forward biased, and the flowing current flows to the amplifier circuit via the diode. Usually, since the amplifier circuit includes a transistor connected to the ground side in the output stage, the current flows to the ground through this transistor. In this way, this power supply circuit has a sink path that allows a part of the current that flows to the load to flow to the ground side, which has not been heretofore, and enables sink operation (with a sink function). It is possible to prevent a situation in which the output voltage cannot be controlled due to the flowing current. In addition, since the sink operation is enabled by adding the diode to the power supply circuit of the series regulator type, an increase in circuit scale can be prevented.

  According to the means described in claim 2, the power supply circuit described in claim 1 is connected via a power supply output line to a functional circuit to which a voltage higher than the target value of the output voltage can be inputted. When a voltage higher than the target value of the output voltage is input to this functional circuit, a current flows out through the power supply output line. Also in the power supply circuit system having such a configuration, the sink operation by the diode according to claim 1 is effective. Therefore, the power supply circuit can control the output voltage to the target value without being affected by the current flowing from the functional circuit to the power supply output line.

  According to the third aspect of the present invention, the functional circuit is configured as a semiconductor integrated circuit device, and when a voltage higher than its own operating power supply voltage is applied to its input terminal, the output voltage of the power supply circuit is changed to its own. The signal at the input terminal is clamped by the action of the clamp circuit supplied as an intermediate voltage lower than the operating power supply voltage. For example, the current from the input terminal to which an external voltage is applied to the power supply output line of the power supply circuit via a parasitic transistor formed on the semiconductor substrate of the semiconductor integrated circuit device due to the operation of the clamp circuit. When the path is formed, a current flows toward the power output line due to the relationship between the voltage of the input terminal and the voltage of the power output line. Thus, even when a current flows into the power output line, the sink operation by the diode according to claim 1 is effective. Therefore, the power supply circuit can control the output voltage to the target value without being affected by the current flowing from the input terminal toward the power supply output line.

Hereinafter, an embodiment of the present invention will be described with reference to FIG.
FIG. 1 shows a schematic configuration of a microcomputer (hereinafter referred to as a microcomputer) mounted on a vehicle ECU (Electronic Control Unit) and its peripheral circuits, and the same components as those in FIG. It is attached.

  A microcomputer 21 (corresponding to a semiconductor integrated circuit device) shown in FIG. 1 includes a reference voltage generation circuit 2, an operational amplifier 3, a diode 22, a voltage detection circuit 5, a clamp circuit 6, power input terminals 7 and 8, a REF terminal 9, and a power output. It is configured as an IC (semiconductor integrated circuit) having a terminal 10 and an input terminal 11. The microcomputer 21 is supplied with an operating power supply voltage VDD (for example, +5 V) via power input terminals 7 and 8 (corresponding to power input lines) and a ground terminal (not shown).

  The series regulator type power supply circuit 13 includes a reference voltage generation circuit 2, an operational amplifier 3 (corresponding to an amplifier circuit), a diode 22 and a voltage detection circuit 5, and a power supply input terminal 7 and a power supply output terminal 10 (power supply output) outside the microcomputer 21. NPN-type transistor 12 (corresponding to the main transistor) connected between them. In addition, a capacitor C1 for stabilizing the output voltage VCL (corresponding to an intermediate voltage, for example, +3 V) at the power supply output terminal 10 is connected between the power supply output terminal 10 and the ground (0 V) outside the microcomputer 21. Has been.

  The output voltage VCL generated at the power output terminal 10 is supplied to the control circuit 24 inside the microcomputer 21 via the power output line 23. The control circuit 24 is supplied with the output voltage VCL and operates in any one of a normal mode in which a normal operation is performed and a low power consumption mode in a standby state.

  The resistors R2 and R3 of the voltage detection circuit 5 are connected between the power output terminal 10 and the ground. The voltage at the common connection point of the resistors R2 and R3, that is, the detection voltage Vdet obtained by dividing the output voltage VCL at the power supply output terminal 10 by the resistors R2 and R3 is applied to the inverting input terminal of the operational amplifier 3. The reference voltage generation circuit 2 is, for example, a band gap reference voltage circuit, and generates a reference voltage Vref for instructing a target value of the output voltage VCL. This reference voltage Vref is given to the non-inverting input terminal of the operational amplifier 3.

  The error amplification signal Sd (corresponding to the drive signal) output from the output terminal of the operational amplifier 3 is given to the base (corresponding to the control terminal) of the transistor 12 via the REF terminal 9, thereby driving the transistor 12. To be controlled. A diode 22 is connected between the power output terminal 10 and the REF terminal 9 with the power output terminal 10 side as an anode. The diode 22 is provided for performing a sink operation described later.

  The clamp circuit 6 (corresponding to a functional circuit) includes transistors P1 to P3. Although FIG. 1 shows only a component for clamping the voltage of the input terminal 11 to the operating power supply voltage VDD side, the clamp circuit 6 is a configuration for clamping the voltage of the input terminal 11 to the ground side. It also has. These transistors P1 to P3 are P-channel MOS transistors. Parasitic diodes D1 to D3 are formed between the source and back gate of each of the transistors P1 to P3 with the source side as an anode. A PNP-type parasitic transistor T1 is formed between the source and drain of the transistor P3. In FIG. 1, the parasitic diodes D1 to D3 and the parasitic transistor T1 are indicated by broken lines.

  In the clamp circuit 6, the source of the transistor P2 is connected to the input terminal 11, and the drain is connected to the power input terminal 8 through the transistor P1. A voltage (Hi) that can control the transistor P1 to be cut off is applied to the gate of the transistor P1. The gate and source of the transistor P3 are connected in common and are connected to the common connection point of the transistors P1 and P2. The drain of the transistor P3 and the gate of the transistor P2 are connected in common and are connected to the power output terminal 10 via the power output line 23. The back gates of the transistors P1 to P3 are all connected to the power input terminal 8.

  The input terminal 11 is connected to a battery power line of a battery voltage + B (corresponding to an external voltage) of +12 V to +16 V via a resistor R1 (for example, several tens of kΩ) outside the microcomputer 21, for example, during vehicle operation, and a switch It is connected to the ground via S1. Therefore, H level (+ B) and L level (0 V) signals are input to the input terminal 11 by turning on and off the switch S1. The signal applied to the input terminal 11 is output to an internal circuit of the microcomputer 21 (not shown).

  In addition to the microcomputer 21, an external component 25 (corresponding to a functional circuit) such as an EEPROM or a CAN (Controller Area Network) driver is mounted on the vehicle ECU. The external component 25 includes a power supply terminal 26 and an external power supply terminal 27. Among these, the battery power line of battery voltage + B is connected to the power terminal 26, while the external power terminal 27 is connected to the power output terminal 10 of the microcomputer 21 through the power output line 28. In the present embodiment, the power supply circuit system 29 is configured by the power supply circuit 13, the clamp circuit 6, and the external component 25.

Next, the operation of this embodiment will be described.
First, the normal operation of the power supply circuit 13 will be described. In the power supply circuit 13, the operational amplifier 3 outputs an error amplification signal Sd corresponding to the difference between the reference voltage Vref applied to the non-inverting input terminal and the detection voltage Vdet applied to the inverting input terminal. The transistor 12 is driven by the error amplification signal Sd, and the output voltage VCL is controlled to a target value shown in the following equation (1). In the following formula (1), the resistance values of the resistors R2 and R3 are shown as R2 and R3, respectively.
Target value = Vref × (R2 + R3) / R3 (1)

  When the power supply circuit 13 is operating as described above, the voltage at the REF terminal 9 is the output voltage VCL + the base-emitter forward voltage VF of the transistor 12. At this time, the diode 22 is reverse-biased and does not affect the control operation of the output voltage VCL by the operational amplifier 3.

  Next, the operation of the clamp circuit 6 when a voltage higher than the operating power supply voltage VDD is applied to the input terminal 11 will be described. Since this clamping operation is disclosed in Japanese Patent Application Laid-Open No. 2004-228707, only a brief description will be given here. The forward voltages of the parasitic diodes D1 to D3 are all set to the voltage VF.

  When the switch S1 is turned off and the battery voltage + B is applied to the input terminal 11 via the resistor R1, the parasitic diode D2 is turned on, and the voltage at the input terminal 11 is a value obtained by adding the voltage VF to the operating power supply voltage VDD. Clamped to (VDD + VF). As a result, an H level (VDD + VF) signal is input to an internal circuit (not shown) of the microcomputer 21.

  In this case, a current Ia (for example, 100 μA to several hundred μA) flows into the microcomputer 21 via the resistor R1 and the input terminal 11. At this time, in the transistor P2, the source is the same as VDD + VF as the input terminal 11, and the gate is the output voltage VCL. Therefore, the threshold voltage VT is secured between the gate and source of the transistor P1, and the transistor P2 is turned on.

  The voltage at the common connection point between the transistors P1 and P2 is clamped to VDD + VF when the parasitic diode D1 is turned on similarly to the parasitic diode D2. Therefore, the source of the transistor P3 becomes VDD + VF. The operating power supply voltage VDD is applied to the back gate of the transistor P3. As a result, the base-emitter voltage of the parasitic transistor T1 of the transistor P3 becomes the voltage VF, and the parasitic transistor T1 is turned on. By such an operation of the clamp circuit 6, a path through which the current Ia flowing from the input terminal 11 into the microcomputer 21 flows into the power supply output line 23 through the transistor P2 and the parasitic transistor T1 is formed.

  Next, the operation of the power supply circuit 13 during the operation of the clamp circuit 6 will be described. When the control circuit 24 of the microcomputer 21 is operating in the normal mode, the consumption current Ib of the control circuit 24 is sufficiently larger than the current Ia flowing from the clamp circuit 6 (Ib >> Ia). For this reason, the current Ia flows to the control circuit 24 operating in the normal mode, and the output voltage VCL of the power supply circuit 13 is controlled to the target value by controlling the driving of the transistor 12, that is, the collector current Ic of the transistor 12.

  On the other hand, when the control circuit 24 of the microcomputer 21 is operating in the low power consumption mode, the current consumption of the control circuit 24 becomes small and the current Ia exceeds the current consumption Ib of the control circuit 24 (Ib <Ia). . Although the output voltage VCL slightly rises from the target value due to the surplus current (Ia-Ib), most of the surplus current flows to the diode 22 as described later, and suppresses the rise of the output voltage VCL.

  That is, the operational amplifier 3 decreases the base voltage of the transistor 12 in order to make the increased output voltage VCL coincide with the target value. When the base voltage of the transistor 12 becomes lower than the output voltage VCL, that is, the emitter voltage of the transistor 12 by the forward voltage VF of the diode 22, the diode 22 is forward biased. As a result, the surplus current flows to the ground via the diode 22 and the transistor (not shown) at the output stage of the operational amplifier 3. That is, the sink operation is performed by the diode 22 and the operational amplifier 3. By such a sink operation, the power supply circuit 13 can control the output voltage VCL as equal to the target value as much as possible without being affected by the surplus current.

  The sink operation by the diode 22 is similarly performed when a current flows from the external component 25 to the power supply circuit 13 through the power supply output line 28. That is, the power supply circuit 13 is connected to a functional circuit to which a voltage higher than the target value of the output voltage VCL can be input via the power supply output line 28, and when this functional circuit receives a voltage higher than the target value. If the current flows through the power output line 28, the sink operation by the diode 22 is effective.

As described above, according to the present embodiment, the following effects can be obtained.
In the series regulator type power supply circuit 13, a diode 22 is connected between the power supply output terminal 10 and the base of the transistor 12 with the power supply output terminal 10 side as an anode. With such a configuration, when current flows from the outside of the power supply circuit 13 to the power supply output line 23 and the output voltage VCL increases beyond the target value, the operational amplifier 3 decreases the base voltage of the transistor 12 and the diode 22 Forward biased. As a result, the current flowing into the power supply output line 23 flows to the ground through the diode 22 and the transistor at the output stage of the operational amplifier 3, and the power supply circuit 13 can output the output voltage VCL to the target value without being affected by the flowing current. Can be controlled. In addition, the sink operation can be performed by adding the diode 22 to a general series regulator type power supply circuit, so that the scale of the power supply circuit 13 can be prevented from increasing.

  The output voltage VCL of the power supply circuit 13 is supplied as an intermediate voltage to the clamp circuit 6 in the microcomputer 21 via the power supply output line 23. When the control circuit 24 of the microcomputer 21 is operating in the normal mode, the consumption current Ib of the control circuit 24 is sufficiently larger than the current Ia flowing into the power supply output line 23 via the input terminal 11 and the clamp circuit 6, and therefore the current Ia Flows to the control circuit 24. However, when the control circuit 24 is operating in the low power consumption mode, the current consumption Ib of the control circuit 24 becomes small and the current Ia exceeds the current consumption Ib. At this time, the output voltage VCL slightly rises from the target value due to the surplus current (Ia-Ib). However, since the sink operation by the diode 22 works effectively, the power supply circuit 13 causes the surplus flowing into the power output line 23. The output voltage VCL can be controlled to be equal to the target value as much as possible without being affected by the current.

  The sink operation by the diode 22 is similarly performed when a current flows from the external component 25 to the power supply circuit 13 through the power supply output line 28. Therefore, the power supply circuit 13 supplies the output voltage VCL as an external power supply to an external component 25 that is mounted on the same vehicle ECU and operates by receiving a battery voltage + B such as an EEPROM or a CAN driver. Is possible.

The present invention is not limited to the embodiment described above and illustrated in the drawings, and the following modifications or expansions are possible.
As shown in FIG. 2, in place of the diode 22 in FIG. 1, the base-emitter of an NPN transistor 41 in the form of a so-called diode connection in which a base and a collector are commonly connected may be used. The same operation and effect as the above can be obtained. In other words, any other element may be used as long as it functions in the same way as a diode, and other elements such as a PNP transistor that forms a diode connection may be used.

The power supply circuit 13 is configured by mounting a circuit other than the transistor 12 on the microcomputer 21, but the circuit mounted on the microcomputer 21 can be changed as appropriate. Further, the power supply circuit 13 may not be mounted on the microcomputer 21 and may be constituted by discrete components.
The main transistor of the power supply circuit 13 may be an N-channel MOS transistor.
The output voltage VCL of the power supply circuit 13, the operating power supply voltage VDD of the microcomputer 21, and the battery voltage + B applied to the input terminal 11 via the resistor R1 are not limited to the values in the above embodiment, but the condition of the following equation (2) It can be appropriately changed to a value satisfying the above. In the following equation (2), the forward voltage of the diode 22 is VF.
VF <VCL <VDD <+ B (2)

  The microcomputer 21 may include a plurality of input terminals 11 to which a voltage higher than the operating power supply voltage VDD may be applied. Further, the semiconductor integrated circuit device is not limited to the microcomputer 21 and may be any device having an input terminal and a functional circuit. The input terminal may be an input / output terminal. The present invention is not limited to a power supply circuit built in a microcomputer mounted in an ECU for a vehicle, and can be applied to a series regulator type power supply circuit in general.

Schematic configuration diagram of a microcomputer and its peripheral circuits showing an embodiment of the present invention FIG. 1 equivalent view showing another embodiment 1 equivalent diagram showing the prior art

Explanation of symbols

  In the drawings, 3 is an operational amplifier (amplifier circuit), 5 is a voltage detection circuit, 6 is a clamp circuit (functional circuit), 7 and 8 are power input terminals (power input lines), 10 is a power output terminal (power output lines), 11 is an input terminal, 12 is a transistor (main transistor), 13 is a power supply circuit, 21 is a microcomputer (semiconductor integrated circuit device), 22 is a diode, 23 and 28 are power supply output lines, 25 is an external component (functional circuit), 29 Is a power supply circuit system.

Claims (3)

An NPN-type or N-channel main transistor interposed between the power input line and the power output line;
A voltage detection circuit that outputs a detection voltage corresponding to an output voltage in the power supply output line;
An amplifier circuit that outputs a drive signal to a control terminal of the main transistor based on a reference voltage corresponding to a target value of the output voltage and the detection voltage;
A power supply circuit comprising a diode connected between the power output line and a control terminal of the main transistor with the power output line side as an anode. A power circuit according to claim 1;
When the external voltage higher than the target value of the output voltage of the power supply circuit is input and connected to the power supply circuit via the power supply output line, and when the external voltage higher than the target value is input And a functional circuit configured to allow current to flow through the power output line. The functional circuit is configured as a semiconductor integrated circuit device,
The semiconductor integrated circuit device includes an input terminal to which an external voltage higher than its operating power supply voltage can be applied, and a clamp circuit that clamps a signal input to the input terminal,
3. The power supply circuit system according to claim 2, wherein an output voltage of the power supply circuit is supplied as an intermediate voltage lower than the operation power supply voltage of the clamp circuit in the clamp circuit.

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