JP2005295706A - Power sequence circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a circuit that can control a voltage between and among a plurality of power supplies not only at power input but also at power cutoff. <P>SOLUTION: When a control signal of a microcomputer 108 is changed to a High level from a Low level, Vfb1 is controlled to be equal to Vref1 (Vfb1=Vref1), and Vfb2 is controlled to be equal to Vref2 (Vfb2=Vref2) by a step-down converter 102 and a step-down converter 120, and a reference voltage value Vref1 is controlled to be larger than a reference voltage value Vref2 (Vref1>Vref2). When the control signal of the microcomputer 108 is changed to the Low level from the High level, the potential Vcht1 of the cathode side of a diode D1 is controlled to be larger than the potential Vcht2 of the cathode side of a diode D2 (Vcht1>Vcht2) by using a proper voltage-dividing resistor. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a power sequence circuit, and more particularly to a power sequence circuit used in an information processing apparatus or the like.

  In recent years, there has been a demand for a power supply system that requires a plurality of power supply voltages in a control controller or information processing apparatus system. In this power supply system, in order to protect the LSI to which power is supplied by the power supply system, it is necessary to pay attention to potential reversal and potential difference between a plurality of power supplies, particularly when the power is turned on / off.

  In a power supply system that requires a plurality of power supply voltages, if the mutual potentials between the power supplies are reversed, not only a malfunction but also a breakdown of the gate oxide film of the MOS transistor and a latch-up phenomenon may occur.

  In such a power supply system, consideration must be given so that the mutual potential between the plurality of power supplies does not reverse when the power is turned on or off. That is, the power supply system operates normally by turning on the power supply having a high voltage value first when turning on the power supply and turning off the power supply having a low voltage value first when turning off the power supply.

There was an invention in which when the power is turned on, soft start is performed to gradually increase the output voltage of the first output circuit, and after the soft start of all the output circuits is completed, the voltage of the output circuit is monitored and circuit protection is performed. (See Patent Document 1).
Japanese Patent Laid-Open No. 10-164825 (page 3, FIG. 1)

  However, since the invention disclosed in Patent Document 1 provides a sequence for the soft start function, it controls the mutual voltage between a plurality of power sources when the power is turned on, but the plurality of times when the power is shut off. The mutual voltage between the power supplies is not controlled.

  Therefore, an object of the present invention is to provide a power sequence circuit capable of controlling the mutual voltage between a plurality of power supplies not only when the power is turned on but also when the power is shut off.

  In order to achieve the above object, according to the first aspect of the present invention, an input power source, a first step-down converter that generates a first voltage value lower than a voltage value of the input power source, and a first voltage value are provided. A first step-down converter that generates a lower voltage value and a first step-down converter, and the first step-down converter is controlled to have the same voltage value during operation. An input terminal, a second input terminal, a first voltage connected to the second input terminal, and a first output terminal provided between the first output terminal provided in the first step-down converter and the ground. The resistor, the second resistor, and the first input terminal are terminals connected between the first resistor and the second resistor, and the first input terminal and the third input terminal And the first step-down converter and the first A control signal generator for generating a control signal to be output to the step-down converter, a third resistor provided between the control signal generator, the first input terminal and the third input terminal, The first diode whose anode side is connected to a side different from the side to which the control signal generator of the resistor is connected, and the first diode connected to a side different from the side to which the control signal generator of the third resistor is connected A first capacitor connected between the anode side of the first diode and the third resistor, a fourth resistor connected to the cathode side of the first diode, and a second step-down converter. And a second voltage connected to the fourth input terminal, the third input terminal being controlled to have the same voltage value during operation of the second step-down converter, the fourth input terminal, and the fourth input terminal. And the second step-down converter The fifth resistor and the sixth resistor provided between the second output terminal and the ground, and the third input terminal are terminals connected between the fifth resistor and the sixth resistor. A second diode whose anode side is connected to a side different from the side to which the control signal generator of the third resistor is connected, and a seventh diode connected to the cathode side of the second diode. And a resistor.

  According to the present invention, it is possible to provide a power sequence circuit that controls the mutual voltage between a plurality of power supplies not only when the power is turned on but also when the power is shut off.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a diagram showing a circuit configuration according to the first embodiment of the present invention.

  FIG. 2 is a diagram illustrating a change in voltage value with time transition of the voltage value of each of the plurality of power supplies.

  A circuit that generates Vcc1, which is a voltage value of one of a plurality of power supplies using the input voltage Vin101, is a step-down converter 102, resistors Rb1 (103), Rc1 (104), which are resistors for monitoring Vcc1, A reference voltage Vref1 generation source (105) is used.

  The step-down converter 102 is a step-down DC-DC converter. The step-down converter 102 is a synchronous rectification step-down DC-DC converter including an input terminal 114 having a feedback voltage Vfb1 and an input terminal 105 having a reference voltage Vref1.

  The step-down converter 102 performs control so that the feedback voltage value Vfb1 and the reference voltage value Vref1 are equal. The step-down converter 102 is connected to a load capacitor CL1 (106) and a load device 107, and can control a positive voltage output.

  The circuit that generates Vcc2 that is the voltage value of one of the plurality of power supplies using the input voltage Vin101 has a circuit configuration similar to the circuit configuration that generates Vcc1, and includes a step-down converter 120, Rb2 (121) and Rc2 (122), which are resistors for monitoring Vcc2, and a reference voltage Vref2 generation source (123).

  The step-down converter 120 is a step-down DC-DC converter, and is a synchronous rectification step-down DC-DC converter including an input terminal 128 having a feedback voltage Vfb2 and an input terminal 123 having a reference voltage Vref1.

  The step-down converter 120 performs control so that the voltage value of the feedback voltage value Vfb2 and the reference voltage value Vref2 are equal. The step-down converter 120 is connected to a load capacitor CL2 (124) and a load device 125, and can control a positive voltage output.

  The power on / off control is performed by the microcomputer 108. The signal output from the microcomputer 108 is output to the resistor R0 (110) via the one gate IC 109. The power source Vcc0, the diode D1 (112), and the anode side of the diode D2 (126) are connected to the end of the resistor R0 that is different from the side to which the IC 109 is connected via the load capacitor C0 (111).

  The feedback terminal 114 of the step-down converter 102 is connected to the cathode side of the diode D1 (112) via the resistor Ra1, and the feedback terminal 128 of the step-down converter 120 is connected to the cathode side of the diode D2 (126) via the resistor Ra2. Is done. Here, the resistor Ra1 may not be connected to the cathode side of the diode D1 (112), and the resistor Ra2 may not be connected to the cathode side of the diode D2 (126).

  When the control signal from the microcomputer 108 is at the low level, the anode side of the diode D1 (112) and the diode D2 (126) is at the ground (Gnd) level, and the diode D1 (112) and the diode D2 (126) are in the reverse bias state. Therefore, no current flows through the resistor Ra1 (113) and the resistor Ra2 (127).

  Therefore, step-down converter 102 and step-down converter 120 perform normal operation (each converter performs control to make the feedback voltage value equal to the reference voltage value), and the voltage values of Vcc1 and Vcc2 are calculated as follows: Is done.

・ Vcc1 = Vref1 × Rc1 / (Rb1 + Rc1)
・ Vcc2 = Vref2 × Rc2 / (Rb2 + Rc2)
Next, consider a case where the control signal output from the microcomputer 108 is changed from the Low level to the High level.

  When the control signal output from the microcomputer 108 is changed from the Low level to the High level, the potentials on the anode side of the diode D1 (112) and the diode D2 (126) are charged with a time constant: resistance R0 × load capacitance C0. Value. When the potential on the anode side of the diode D1 (112) becomes larger than the sum of the voltage value Vf1 applied to the resistor Ra1 (113) and the feedback voltage value Vfb1, the resistor Ra1 from the cathode side of the diode D1 (112). Current begins to flow.

  When the value of the current flowing into the resistor Ra1 (113) from the cathode side of the diode D1 (112) increases, the step-down converter 102 controls the reference voltage value Vref1 and the feedback voltage value Vfb1 to be equal to each other. The current that flows into the resistor Ra1 (113) from the cathode side of D1 (112) flows into the load device 107 via the resistor Rb1 (102).

  As the amount of current flowing into resistor Rb1 (103) increases, the value of voltage value Vcc1 decreases. When the voltage value Vcc1 continues to decrease and reaches the Gnd level, and the voltage value Vcc1 further decreases, the step-down converter 102 becomes negative output control and becomes uncontrollable.

  When step-down converter 102 is in an uncontrollable state, it is impossible to perform control to make feedback voltage value Vfb1 equal to reference voltage value Vref1, and therefore feedback voltage value Vfb1 is larger than reference voltage value Vref1. .

  The operation when the current starts to flow in the forward direction of the diode D2 (126) is the same as the operation when the current starts to flow in the forward direction of the diode D1 (112) described above.

  Therefore, when the step-down converter 102 and the step-down converter 120 are in normal operation, the feedback voltage value Vfb1 = reference voltage value Vref1, the feedback voltage value Vfb2 = reference voltage value Vref2, and the voltage value applied to the resistor Ra1 (113). If the voltage value Vf2 applied to Vf1 and the resistor Ra2 (127) is substantially the same value, by controlling the reference voltage value Vref1> the reference voltage value Vref2, the Vcc2 cutoff start timing is started as shown in FIG. It becomes possible to start earlier than the time.

  Next, consider a case where the control signal output from the microcomputer 108 is changed from High level to Low level.

  When the control signal output from the microcomputer 108 is changed from a high level to a low level, the potential on the anode side of the diode D1 (112) and the diode D2 (126) is discharged by a time constant: resistance R0 × load capacitance C0. Value.

  Since the anode-side potential of the diode D1 (112) decreases with time, the amount of current flowing from the diode D1 (112) to the resistor Ra1 (113) decreases with time. Therefore, the feedback voltage value Vfb1 also decreases with the passage of time. When the feedback voltage value Vfb1 reaches the reference voltage value Vref1, the step-down converter 102 can be controlled, and the voltage value Vcc1 starts to increase.

  The operation when the potential on the anode side of the diode D2 (126) decreases with the passage of time is the same as the operation described above when the potential on the anode side of the diode D1 (112) decreases with the passage of time. It is.

  The potential Vcth1 on the cathode side of the diode D1 (112) and the potential Vcth2 on the cathode side of the diode D2 (126) when Vcc1 and Vcc2, which are voltage values of one of the plurality of power supplies, start to increase from 0 are Is calculated as follows.

Vcth1 = Vref1 × (Ra1 × Rb1 + Ra1 × Rc1 + Rb1 × Rc1) / (Rb1 × Rc1) (1)
Vcth2 = Vref2 × (Ra2 × Rb2 + Ra2 × Rc2 + Rb2 × Rc2) / (Rb1 × Rc1) (2)
Therefore, by setting Vcht1> Vcht2 using an appropriate voltage dividing resistor, it is possible to start the power-on start time of Vcc1 earlier than the power-on start time of Vcc2, as shown in FIG.

  An example of a suitable voltage dividing resistor is R0 = 2 kΩ, C0 = 0.5 μF, Ra1 = 2 kΩ, Ra2 = 10 kΩ, Rb1 = 10 kΩ, Rb2 = 20 kΩ, Rc1 = 10 kΩ, Rc2 = 20 kΩ, Vref1 = 1.65 V By setting Vref2 = 0.9V, as shown in FIG. 2, when power is turned on, Vcc1, which is a power supply having a high voltage value, rises first, and then Vcc2, which is a power supply having a low voltage value, is supplied. stand up. In addition, when the power is shut off, Vcc2, which is a power supply having a low voltage value to be supplied, first falls, and thereafter, Vcc1 which is a power supply having a high voltage value to be supplied falls.

  By controlling the power supply system described above, a power supply having a high voltage value can be constantly maintained at a high voltage value compared to a power supply having a low voltage value to be supplied. It becomes possible to prevent reversal. Next, a second embodiment will be described with reference to FIG.

  FIG. 3 is a diagram showing a circuit configuration according to the second embodiment of the present invention.

  The circuit configuration according to the second embodiment is a configuration in which a load capacitor C1 (230) and a resistor R1 (231) are added as compared with the circuit configuration according to the first embodiment. The load capacitor C1 (230) is connected to the power supply Vcc0, and the resistor R1 (231) is connected to the one-gate IC 109.

  In the first embodiment described with reference to FIG. 1, the current flowing into the diode D1 (112) and the current flowing into the diode D2 (126) are both supplied via the resistor R0 (110). Therefore, when the forward voltages of the diode D1 and the diode D2 are largely different due to the manufacturing variation of the diode, there is a possibility that the potential of the power supply Vcc1 does not completely drop to Gnd when the power supply is cut off.

  Therefore, by adding the load capacitor C1 (230) and the resistor R1 (231), it is possible to change the rise and fall timings at the time of turning on / off the power of Vcc1 and Vcc2. Next, a third embodiment will be described with reference to FIG.

  FIG. 4 is a diagram showing a circuit configuration according to the third embodiment of the present invention.

  The circuit configuration according to the third embodiment is a configuration in which the reference voltage value Vref is connected to the step-down converter 302 and the step-down converter 320 as compared with the circuit configuration according to the first embodiment.

  In this case, the falling start timing of power shutoff is the same for Vcc1 and Vcc2, and the rising start timing at power on is the resistors Ra1 (312), Ra2 (327), and Rb1 (in Equations (1) and (2)). 303), Rb2 (321), Rc1 (304), and Rc2 (322) are appropriately selected so that Vcth> Vcth2, and as shown in FIG. Vcc1 rises first, and then Vcc2, which is a power supply with a low voltage value to be supplied, rises.

  Furthermore, by setting a value of a time constant: resistance R0 × load capacitance C0 so that the step-down converter reliably controls the rising and falling of the voltage of each of the plurality of power supplies, the mutual potential between the power supplies is set. It is possible to reliably prevent the reverse rotation.

  By setting the values of the load capacitor C0 and the resistor R0 to appropriate values, the rising and falling speeds of the voltages of the plurality of power supplies can be adjusted. In a system in which the time from the start of voltage to the start of operation is specified, by selecting a load capacitor C0 and a resistor R0 having relatively large values that reach an appropriate voltage value by the start of operation, Vcc1> It becomes possible to maintain Vcc2. Further, since the step-down converter itself is in an enabled state, it is not necessary to consider the time required to start the step-down converter.

  The present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

1 is a diagram showing a circuit configuration according to a first embodiment of the present invention. The figure which shows the voltage value change accompanying the time transition of the voltage value of each of several power supply. The figure which shows the circuit structure based on the 2nd Embodiment of this invention. The figure which shows the circuit structure based on the 3rd Embodiment of this invention.

Explanation of symbols

102, 120 ... step-down converter, 107, 125 ... load device,
108: microcomputer, 112, 126 ... diode,

Claims (4)

Input power,
A first step-down converter that generates a first voltage value lower than the voltage value of the input power supply;
A second step-down converter that generates a voltage value lower than the first voltage value;
A first input terminal and a second input terminal which are provided in the first step-down converter and are controlled so that the first step-down converter has the same voltage value during operation;
A first voltage connected to the second input terminal;
A first resistor and a second resistor provided between a first output terminal provided in the first step-down converter and a ground;
The first input terminal is a terminal connected between the first resistor and the second resistor,
A control signal generating unit that is connected to the first input terminal and the third input terminal and generates a control signal output to the first step-down converter and the second step-down converter;
A third resistor provided between the control signal generator and the first input terminal and the third input terminal;
A first diode having an anode connected to a side different from a side to which the control signal generating unit of the third resistor is connected;
A first resistor connected to a side of the third resistor different from a side to which the control signal generator is connected and connected between the anode side of the first diode and the third resistor; A capacitor,
A fourth resistor connected to the cathode side of the first diode;
A third input terminal and a fourth input terminal which are provided in the second step-down converter and are controlled such that the second step-down converter has the same voltage value during operation;
A second voltage connected to the fourth input terminal;
A fifth resistor and a sixth resistor provided between a second output terminal provided in the second step-down converter and the ground;
The third input terminal is a terminal connected between the fifth resistor and the sixth resistor,
A second diode having an anode connected to a side different from a side to which the control signal generating unit of the third resistor is connected;
A seventh resistor connected to the cathode side of the second diode;
The power sequence circuit, wherein the first step-down converter and the second step-down converter are synchronous rectification step-down converters. Input power,
A first step-down converter that generates a first voltage value lower than the voltage value of the input power supply;
A second step-down converter that generates a voltage value lower than the first voltage value;
A first input terminal and a second input terminal which are provided in the first step-down converter and are controlled so that the first step-down converter has the same voltage value during operation;
A first voltage connected to the second input terminal;
A first resistor and a second resistor provided between a first output terminal provided in the first step-down converter and a ground;
The first input terminal is a terminal connected between the first resistor and the second resistor,
A control signal generating unit that is connected to the first input terminal and the third input terminal and generates a control signal output to the first step-down converter and the second step-down converter;
A third resistor provided between the control signal generator and the first input terminal and the third input terminal;
A first diode having an anode connected to a side different from a side to which the control signal generating unit of the third resistor is connected;
A first resistor connected to a side of the third resistor different from a side to which the control signal generator is connected and connected between the anode side of the first diode and the third resistor; A capacitor,
A third input terminal and a fourth input terminal which are provided in the second step-down converter and are controlled such that the second step-down converter has the same voltage value during operation;
A second voltage connected to the fourth input terminal;
A fourth resistor and a fifth resistor provided between a second output terminal provided in the second step-down converter and the ground;
The third input terminal is a terminal connected between the fourth resistor and the fifth resistor,
A second diode having an anode connected to a side different from a side to which the control signal generator of the third resistor is connected;
The power sequence circuit, wherein the first step-down converter and the second step-down converter are synchronous rectification step-down converters. An eighth resistor connected between the control signal generator and the third input terminal and connected to the anode side of the second diode;
The apparatus further comprises a second capacitor connected between a side of the eighth resistor different from a side to which the control signal generating unit is connected and an anode side of the second diode. Item 3. The power sequence circuit according to Item 1 or 2. 3. The power sequence circuit according to claim 1, wherein the first voltage and the second voltage are a common voltage.

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