JP2016181071A - Power supply - Google Patents

Abstract

The conventional power supply apparatus has a problem that when the negative feedback signal Vfb1 of the output voltage Vout is disconnected, the output voltage Vout increases and the electronic load 8 is destroyed. There was also a problem that the disconnection could not be diagnosed. In order to solve the above-mentioned problems, the present invention has a pull-up current at a negative feedback terminal 10 and, at the time of disconnection, the output voltage Vout is reduced to 0 V by a negative feedback operation. Further, from the result of the abnormality diagnosis comparator 6 when the pull-up current 1 is turned ON / OFF, it is possible to diagnose whether the negative feedback signal Vfb1 rises due to disconnection or an external voltage short circuit. [Selection] Figure 1

Description

  The present invention relates to a power supply device that generates a constant voltage from a supplied voltage, and more particularly to a power supply device mounted on an in-vehicle electronic control device.

  Various in-vehicle electronic control devices have been proposed that output a constant voltage from a battery. These power supply devices have a mechanism for controlling the output voltage with high accuracy and constant by negatively feeding back the output voltage. For example, a power supply device shown in Patent Document 1 is known.

JP 2012-160048 A

  In a conventional power supply device, if the negative feedback signal is in an abnormal state such as disconnection, the output voltage cannot be controlled to a desired voltage, and the electronic load such as a microcomputer connected to the output may be destroyed. . A vehicle-mounted electronic control device is required to have extremely high safety, and it is required to avoid various controls being disabled due to destruction of a microcomputer or the like.

  FIG. 8 shows the configuration of a conventional power supply device. This power supply device includes a reference voltage Vref1 and an error amplifier 4 that amplifies the reference voltage Vref1, an output driver 11, and feedback resistors R1 and R2. An electronic load 8 is connected to the output voltage Vout of the power supply device. This power supply device amplifies the reference voltage Vref1 by an amplification factor (R1 + R2) / R1 determined by feedback resistors R1 and R2, and controls output of a constant output voltage Vout = Vref1 × (R1 + R2) / R1.

  Here, when the negative feedback signal Vfb1 from the output voltage Vout is disconnected, the negative feedback signal Vfb1 does not match the output voltage Vout, so the negative feedback amplification by the error amplifier 4 cannot be performed, and the desired output voltage Vout is controlled. It becomes impossible. As shown in FIG. 8, when feedback resistors R1 and R2 are provided inside IC3, error amplifier inverting input voltage Vfb2 becomes 0 V when disconnection occurs, so that output voltage Vout rises to near the VS1 voltage by the amplification operation of error amplifier 4. At this time, if the output voltage Vout exceeds the maximum rating of the electronic load 8 such as a connected microcomputer, the electronic load 8 is destroyed. Further, the conventional power supply device has a problem that it cannot diagnose an abnormality such as the disconnection of the negative feedback signal Vfb1.

  The present invention has been made in view of such problems, and an object thereof is to avoid the destruction of the electronic load when an abnormality such as a disconnection occurs and to diagnose the abnormal state.

  In the present invention, the pull-up current 1 is first connected to the negative feedback terminal 10 as shown in FIG. Set feedback resistor R1 and pull-up current 1 so that error amplifier 4 inverted input voltage Vfb2 exceeds reference voltage Vref1 when disconnection occurs. Next, a switch that can control ON / OFF of the pull-up current 1 is provided. In addition, an abnormality diagnosis comparator 6 is provided for detecting an inverted input voltage of the error amplifier 4 when the pull-up current is turned ON / OFF. Further, a control unit 5 for judging an abnormal state from the output result of the abnormality diagnosis comparator 6 and a register 7 for holding the result are provided.

  By the above means, when the negative feedback signal Vfb1 is disconnected, the inverting input voltage Vfb2 of the error amplifier 4 becomes higher than the reference voltage Vref1, so that the output voltage Vout is controlled to decrease to 0V by the amplification operation of the error amplifier 4, and the electronic load 8 Can be prevented. In addition, a switch that can control pull-up current 1 ON / OFF can prevent leakage current from VS2 when Vout is turned off.

  Also, when the abnormality diagnosis comparator 6 is detected, the pull-up current is turned on and off to compare the change in the detection result of the abnormality diagnosis comparator 6 to diagnose the disconnection of the negative feedback signal Vfb1 and the occurrence of an external voltage short circuit The diagnosis result can be held in the diagnosis register 7.

It is a block diagram of the power supply device which is the 1st Example of this invention. FIG. 3 is a configuration diagram of a power supply device according to a second embodiment of the present invention. 3 is a timing chart when a disconnection occurs during operation in the first embodiment. 6 is a timing chart when an operation is started after disconnection in the first embodiment. FIG. 6 is a switch operation diagram of an abnormality diagnosis pull-up current in the first embodiment. 6 is a diagnosis timing chart when disconnection occurs in the first embodiment. FIG. 3 is a diagnosis timing chart when an external voltage short-circuit occurs in the first embodiment. It is a block diagram of the conventional power supply device.

  Hereinafter, embodiments will be described with reference to the drawings.

  FIG. 1 is a configuration diagram of a power supply apparatus using the output driver 11 and IC3 according to the first embodiment. The power supply device steps down an input voltage of, for example, a vehicle-mounted battery to a predetermined voltage such as an internal circuit supply voltage of the vehicle-mounted control device.

  IC3 of this embodiment includes an error amplifier 4 and an output driver 11 that amplify the difference voltage between the reference voltage Vref1 and the inverted input voltage Vfb2, a feedback resistor 6 and 7 that sets the amplification degree, a pull-up current 1, and a pull-up thereof. It comprises a switch 2 that controls the current 1, an abnormality diagnosis comparator 6, a control unit 5, and a diagnosis register 7. An electronic load 8 is connected to the output voltage Vout of the power supply device. This power supply device amplifies the reference voltage Vref1 with an amplification factor (R1 + R2) / R1 determined by the feedback resistors R1 and R2, and controls it to a constant output voltage Vout = Vref1 × (R1 + R2) / R1.

  FIG. 3 shows a timing chart when disconnection occurs during normal operation. The solid line represents the operation of the proposed first embodiment, and the dotted line represents the operation of the conventional configuration in FIG. When the activation signal PSA for activating the power supply device is turned on, the control signal 1 for controlling the error amplifier 4 and the control signal 2 for the switch 2 for flowing the pull-up current 1 are turned on in synchronization therewith. The error amplifier 4 starts an amplifying operation by the control signal 1, and the output voltage Vout of the power supply device gradually rises to a desired voltage of Vref1 × (R2 + R1) / R1. In the conventional circuit of FIG. 8, the operation indicated by the dotted line is performed as described above, and the output voltage Vout rises to VS1, and the electronic load 8 may be destroyed.

  Next, in the embodiment of FIG. 1, when disconnection occurs, the negative feedback signal Vfb1 of the negative feedback terminal 10 becomes Ipull × (R1 + R2) from the pull-up current 1 and the feedback resistors 6 and 7. Further, the inverting input voltage Vfb2 of the error amplifier 4 becomes Ipull × R1, and by setting Ipull so that this voltage becomes larger than Vref1, the inverting input voltage Vfb2 becomes higher than that during normal operation at the time of disconnection. When this high voltage is input to the error amplifier 4, the output voltage Vout decreases to 0V as shown by the solid line in FIG. The electronic load 8 connected to the output of the power supply unit uses the output of the power supply unit as a power supply voltage or reference voltage, and when the disconnection occurs, this voltage drops to 0V to avoid destruction of the electronic load 8 I can do it.

  Here, the pull-up current 1 needs to be a current proportional to Vref1 / R1 so as not to be affected by the change of the feedback resistance. Further, it is necessary to set the current smaller than the current consumed by the electronic load 8 during normal operation. Further, the pull-up current 1 can be replaced with a pull-up resistor. In this case, it is necessary to set the VS2 voltage and the pull-up resistor so as to exceed the negative feedback voltage Vfb2 of the error amplifier 4 at the time of disconnection.

  FIG. 4 shows a timing chart when the disconnection state occurs before the activation signal PSA is turned ON. The solid line represents the operation of the proposed first embodiment, and the dotted line represents the operation of the conventional configuration in FIG. In the conventional configuration of FIG. 8, the output voltage Vout similarly rises to near VS1, and there is a possibility of destruction of the electronic load 8, but in the case of Example 1, the output voltage Vout is maintained at 0 V, so that the destruction can be avoided. . Here, FIG. 5 shows a timing chart of the switch 1 for controlling ON / OFF of the pull-up current 1. When this power supply is in a standby state (when Vout is off), the output leakage current is set to 0, so that the pull-up current 1 is turned off by the switch 2 in accordance with the control signal 2 for controlling the switch. The control signal 2 is also OFF when the activation signal PSA is OFF.

  This also has an effect of preventing leakage current from continuing to flow through the external electronic load 8 even when the power supply device is on standby.

  Next, a disconnection state diagnosis method will be described. FIG. 6 shows a diagnosis timing chart when disconnection occurs. As described with reference to FIG. 3, the negative feedback voltage Vfb2 at the time of disconnection is a voltage of Ipull × R1. At this time, by setting the reference voltage 12 (Vref2) of the abnormality diagnosis comparator 6 as Vref1 <Vref2 <Ipull × R1, it is possible to detect the voltage at the time of disconnection. On the other hand, as another condition detected by the abnormality diagnosis comparator 6, an external voltage short circuit to the output voltage Vout can be considered. In order to determine whether the detection of the abnormality diagnosis comparator 6 is due to disconnection or external voltage short-circuit, as shown in the timing chart of FIG. It can be judged from the change in the output result of 6. As shown in FIG. 6, if the output of the abnormality diagnosis comparator 6 is in a detection state for a certain time, it can be determined that a disconnection or an external voltage short-circuit has occurred, so the control signal 1 of the error amplifier 4 is turned OFF. If the output of the abnormality diagnosis comparator 6 does not change for a certain period of time with the control signal 1 turned off, the control signal 2 is further turned off. By turning off the control signal 2, the pull-up current 1 is turned off, so if it is disconnected, the negative feedback voltage Vfb2 will be 0V and the output of the abnormality diagnosis comparator 6 will not be detected, thus diagnosing the disconnected condition. Determine. On the other hand, in the case of an external voltage short circuit, the detection result of the abnormality diagnosis comparator 6 is maintained even after the control signal 2 is turned off as shown in FIG.

  In order to judge this disconnection and external voltage short, it is necessary to turn off the power supply function completely, but it is also possible to perform only diagnosis of disconnection or external voltage short while keeping control signals 1 and 2 ON. Is possible.

  As a result, disconnection / external voltage short-circuit can be determined, and in the case of temporary disconnection or external voltage short-circuit, it is possible to control to return to normal output after recovery from an abnormal state. .

  FIG. 2 shows a power supply device having a step-down switching regulator according to the second embodiment. In the case of the switching regulator configuration, the configuration for negative feedback control from the output voltage Vout is the same, and the same configuration described in the first embodiment by adding the same configuration of the pull-up current 1, the switch 2, and the abnormality diagnosis comparator 6 is the same. An effect is obtained.

  The same applies to the step-up side switching regulator.

1 Pull-up current 2 Switch 3 IC
4 Error amplifier 5 Control unit 6 Abnormality diagnosis comparator 7 Diagnostic register 8 Electronic load 9 Error amplifier output terminal 10 Negative feedback terminal 11 Output driver 12 Inductor 13 Capacitor 14 PWM control unit 15 Switching regulator driver unit 16 Switching regulator output terminal
Vout Power supply output voltage
Vref1 Error amplifier reference voltage
Vref2 Abnormality diagnosis comparator reference voltage
R1, R2 Feedback resistor
VS1 Output driver power supply voltage
VS2 Pull-up current supply voltage
Verr Error amplifier output voltage
Negative feedback signal for Vfb1 power supply
Vfb2 Error amplifier inverting input signal
PSA power supply activation signal

Claims (5)

In a power supply device that generates a predetermined output voltage from an input voltage and feeds back a negative feedback signal related to the output voltage,
A pull-up circuit connected to the signal line of the negative feedback signal;
The pull-up circuit reduces the output voltage by making the negative feedback signal higher than a predetermined voltage when the negative feedback signal is abnormal. The power supply device according to claim 1,
A power supply apparatus comprising switch means for ON / OFF control of the pull-up circuit. The power supply device according to claim 1 or 2, wherein:
A comparator for comparing the negative feedback signal with a predetermined voltage;
A power supply apparatus characterized by diagnosing a disconnection state or an external short-circuit state of the negative feedback signal by the comparator. The power supply device according to claim 3,
A power supply apparatus comprising a register for storing a result of diagnosing a disconnection state or an external short state of the negative feedback signal. An in-vehicle control device comprising at least one power supply device according to claim 1 for controlling an in-vehicle device,
The vehicle-mounted control device, wherein the input voltage is a voltage of a vehicle-mounted battery and the output voltage is a supply voltage for an internal circuit of the vehicle-mounted control device.

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