JP5417722B2 - Charge pump circuit - Google Patents

Description

  The present invention relates to a charge pump circuit that is provided in an electronic device that requires a negative voltage and generates a negative voltage from a positive voltage.

  Negative voltages are used in LCD (Liquid Crystal Display) panels and organic EL (Electroluminescence) displays, and high-accuracy negative voltages are required in various devices.

  Conventionally, there are two configurations of a negative voltage generation circuit, a switching regulator and a charge pump.

  By the way, conventionally, in a switching regulator, a soft start circuit is employed in order to prevent destruction or malfunction of a switching transistor or an IC serving as a load of the switching regulator due to a rush current for charging an output capacitor at start-up.

  A negative voltage output switching regulator having a soft-start function has been proposed in Japanese Patent Application Laid-Open No. H10-228707.

  FIG. 13 is a circuit diagram showing a switching power supply using a negative voltage output switching regulator having a soft start function disclosed in Patent Document 1. As shown in FIG. 13, a switching power supply (switching circuit) 100 includes a soft start circuit 101, a triangular wave generation circuit 102, an error amplifier (error amplification circuit) 103, a comparator (comparison circuit) 104, and a drive unit (drive circuit) 105. , A voltage dividing circuit 106 including a switching transistor (switching element) Tr1, a diode D, a coil L, capacitors C1 and C2, and resistors R1 and R2. Here, the switching power supply controller 107 includes a soft start circuit 101, a triangular wave generation circuit 102, an error amplifier 103, a comparator 104, and a drive unit 105. The output stage 108 includes a switching transistor Tr1, a diode D, a coil L, and a capacitor C1. Here, the voltage dividing circuit 106 has a function of dividing the output voltage of the soft start circuit 101 and the output voltage (Vo) of the output terminal Vo. The capacitor C2 is a soft start period adjustment circuit.

According to the above switching power supply, a soft start function can be provided and a stable negative voltage output can be provided. In addition, it is possible to operate the feedback function in the circuit immediately after power activation, to prevent negative overshoot of negative voltage output at power activation, and to load side circuit elements that output negative voltage You can eliminate the damage to you.
JP 2006-158055 A

  As described in Patent Document 1, a switching regulator that outputs a negative voltage has been proposed that has a soft start function. However, an inversion mode charge pump circuit that outputs a negative voltage using a soft start function is not known. Even in the charge pump circuit in the inversion mode, there is a problem such as overshoot on the negative side of the negative voltage output at the time of starting the power supply.

  An object of the present invention is to provide a charge pump circuit having a soft start function in order to solve the above-described problems.

The voltage inversion type charge pump circuit according to the present invention includes a voltage source, first and second rectifier elements connected in series between a ground and an output terminal, an output capacitor connected to the output terminal, A flying capacitor connected to a connection point between the first and second rectifier elements, a first switch means having switch elements that are alternately turned on and off, and a second switch connected to the first switch means Means, a drive circuit for driving the first switch means, and a control circuit for adjusting the on-resistance of the second switch means to control the output voltage of the output capacitor, the control circuit having an output having an error amplifier for amplifying an error between the voltage and the target value, supplied to the non-inverting side input of said error amplifier and an output voltage and a reference voltage of the output terminal by dividing, soft to the inverting side input of said error amplifier The output of the output circuit is given as a predetermined negative voltage by giving the output of the start circuit and the output of the soft start circuit falling at a constant rate from the reference voltage potential or the ground potential to a predetermined negative voltage potential. It is controlled .

  According to the present invention, the second switch means is an N-channel MOS transistor provided between the first switch means and the ground, and the output of the error amplifier is connected to the N-channel MOS transistor. Can be configured to feed the gate.

The present invention further includes voltage dividing means for dividing the output voltage of the soft start circuit and the output voltage of the output terminal , and the output from the voltage dividing means is input to the non-inverting side input or inverted. The soft start circuit can be configured to increase from a ground potential to a reference potential at a constant rate.

  According to the present invention, the second switch means is an N-channel MOS transistor provided between the first switch means and the ground, and the voltage dividing means is connected to the non-inverting side input of the error amplifier. And the inversion side input is set to the ground potential, and the output of the error amplifier is supplied to the gate of the N-channel MOS transistor.

  According to the present invention, the second switch means is a P-channel MOS transistor provided between the first switch means and a voltage source, and the voltage dividing means is connected to the inverting side input of the error amplifier. The non-inverting side input is set to the ground potential, and the output of the error amplifier is given to the gate of the P-channel MOS transistor.

  According to the present invention, an inversion type charge pump having a soft start function can be realized, and the feedback function in the circuit is operated immediately after the power supply is started, so that a negative overshoot on the negative voltage output at the time of power supply start-up can be achieved. Therefore, it is possible to prevent damage to the circuit element on the load circuit side where a negative voltage is output.

  Embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and the description thereof will not be repeated in order to avoid duplication of description.

  FIG. 1 is a block circuit diagram showing a charge pump circuit adopting an inversion mode for outputting a negative voltage in the first embodiment of the present invention.

  In FIG. 1, an inversion mode type charge pump circuit includes a first switch means 13 connected to a power supply voltage VDD, a second switch means having one end connected to the switch means 13 and the other end grounded (GND). 14, a diode 21, a diode 22, a flying capacitor 12, an output capacitor 11, an oscillation circuit 16, an error amplifier 15, a feedback resistor 19, a voltage dividing circuit including a feedback resistor 20, a reference power supply 18, and a soft start circuit 17.

  The positive terminal of the flying capacitor 12 is connected to the power supply voltage VDD via the first switch means 13, and the negative terminal is grounded via the diode 21. The positive terminal of the output capacitor is connected to the negative terminal of the flying capacitor 12 via the diode 22, and the negative terminal is grounded.

  Although not shown, the first switch means 13 is provided with two switch elements, and the two switch elements are alternately turned on and off by a signal from the oscillation circuit 16. For example, the two switch elements include a P channel type (hereinafter referred to as P type) MOS transistor on the power supply voltage side, and an N channel type (hereinafter referred to as N type) MOS transistor on the ground (GND) side. It is configured to be turned on and off alternately by the signal of the oscillation circuit 16.

  The second switch means 14 is composed of, for example, an N-type MOS transistor, and becomes active when the ground-side switch of the first switch means 13 is turned on, and the operation is controlled by the first switch means 13. As will be described later, a signal from the error amplifier 15 is given to the gate of the N-type MOS transistor constituting the second switch means 14, and the on-resistance of the N-type MOS transistor is adjusted by the signal from the error amplifier 15. Is done.

  The feedback resistor 19 is connected to the output terminal Vo, and the feedback resistor 20 is connected to the reference power supply (Vref) 18.

  The error amplifier 15, the feedback resistors 19 and 20, the reference power supply 18, and the soft start circuit 17 constitute a control circuit that controls the output voltage.

  The first switch means 13 and the second switch means 14 control the charging of the flying capacitor 12 and the operation of charging the output capacitor 11 by inverting the voltage charged in the flying capacitor 12.

The signal from the first switch means 13 is oscillating circuit 16, the power source side of the switching element is turned on, then off the ground side switching element, and, MOS transistor 14 as a second switching means is turned off At this time, the power supply voltage VDD and the flying capacitor 12 are connected in series via the first switch means 13, and the flying capacitor 12 is charged via the first switch means 13 and the diode 21.

  When the first switch means 13 is turned off by the signal from the oscillation circuit 16 and the switch element on the ground side is turned on and the switch element on the ground side is turned on, the second switch 14 is activated (on), and the flying capacitor 12 The positive terminal is grounded via the first switch means 13 and the second switch means 14, the voltage charged in the flying capacitor 12 is inverted, and the output capacitor is inverted via the second switch 14 and the diode 22. 11 is charged and a negative voltage is generated.

  The output of the error amplifier 15 is given to the gate of the N-type MOS transistor as the second switch means 14. The error amplifier 15 outputs a control signal obtained by amplifying the error between the output voltage and the target value.

  In the first embodiment, the non-inverting input of the error amplifier 15 is given an output obtained by dividing the output voltage Vo of the output terminal Vo and the reference voltage Vref of the reference power supply 18, and the inverting input is soft-started. The output of circuit 17 is provided. The soft start circuit 17 drops at a constant rate from the reference voltage Vref level to the ground (GND) level during the soft start period.

  FIG. 2 is a block circuit diagram showing an example of a soft start circuit in the circuit shown in FIG. The soft start circuit 17 includes a constant current source 171, a switching transistor 172, a reference voltage source 173, a switch 174, and a capacitor C2. The capacitor C2 adjusts the soft start period and functions as a soft start adjustment period.

  In the soft start circuit 17, the switch 174 is controlled so that the capacitor C2 is connected to the reference voltage source 173 side before the power supply is started, and the capacitor C2 is connected to the constant current source 171 after the power supply is started. In the soft start circuit 17, the capacitor C2 is charged to the reference voltage Vref when the power supply is activated. The potential on the upper side of the capacitor C2 is Vref. After the power is turned on, a negative voltage is charged from the constant current source 171 to the capacitor C2 with a constant current. Therefore, as shown in FIG. 3, the potential of the capacitor C2 decreases in proportion to time at a constant rate. Go. When this voltage reaches ground (GND), it is maintained at a constant voltage (GND).

  When the inverting input (reference side) of the error amplifier 15 is used as the output of the soft start circuit 17, the inverting input (reference side) is normally set to the GND level at the steady state after the soft start. The potential difference between the output voltage at the output terminal Vo and the reference potential Vref is divided by the feedback resistor 19 and the feedback resistor 20, and the output is given to the non-inverting input of the error amplifier 15.

  The on-resistance of the second switch 14 is controlled by the output of the error amplifier 15, and the output voltage is controlled to be a target value voltage.

  FIG. 3 is a diagram showing the relationship between the output of the soft start circuit 17 and the output voltage Vo. As shown in FIG. 3, as the output of the soft start circuit 17 decreases at a constant rate, the value of the inverting input of the error amplifier 15 changes at a constant rate. As a result, the ON resistance of the second switch 14 is controlled by the output of the error amplifier 15, the output voltage Vo is controlled, and the negative potential increases at a constant rate. When the soft start circuit 17 becomes a constant voltage, the output voltage of the output voltage Vo is output as a predetermined negative voltage according to this voltage. By this feedback control, an inversion type charge pump having a soft start function can be realized. In addition, it is possible to operate the feedback function in the circuit immediately after power activation, to prevent negative overshoot of negative voltage output at power activation, and to load side circuit elements that output negative voltage Can be prevented from being damaged.

  By the way, as described above, when the inverting input (reference side) of the error amplifier 15 is used as the output of the soft start circuit 17 and the reference side is set to the GND level in the steady state after the soft start, the following problems may occur. is there. That is, when the output of the soft start circuit 17 falls from the Vref to the GND level in the charge pump circuit in which the reference voltage (Vref) is set to the ground (GND) and is often a negative voltage output in a steady state, the error amplifier When the inverting input (reference side) of 15 is a voltage close to the GND level and the impedance is high, it is likely to be affected by noise and the output voltage may vary.

  Therefore, the second embodiment of the present invention solves the difficulty of the first embodiment. FIG. 4 is a block circuit diagram showing a charge pump circuit adopting an inversion mode for outputting a negative voltage in the second embodiment of the present invention. In addition, the same code | symbol is attached | subjected to the same component as FIG. 1, and the description of an overlapping part is omitted.

  In the second embodiment shown in FIG. 4, the output voltage Vo of the charge pump circuit and the output of the soft start circuit 17a are divided to feed back the voltage.

  In the second embodiment shown in FIG. 4, a soft start circuit 17 a is connected to the feedback resistor 20, and the output voltage of the soft start circuit 17 a and the output voltage (Vo) of the output voltage terminal Vo are fed back by the feedback resistors 19 and 20. Divide pressure.

  In the second embodiment, the non-inverting input of the error amplifier 15 is supplied with the output voltage Vo of the output terminal Vo and the output divided by the soft start circuit 17a, and the inverting input is grounded as a reference voltage (GND). ) Is given. The soft start circuit 17a rises at a constant rate from the ground (GND) level to the reference voltage (Vref) level during the soft start period.

  FIG. 5 is a block circuit diagram showing an example of the soft start circuit of FIG. The soft start circuit 17a includes a constant current source 171a, a switching transistor 172, a clamp circuit 175, and a capacitor C2. The capacitor C2 adjusts the soft start period and functions as a soft start adjustment period.

In the soft start circuit 17, since the electric charge accumulated in the capacitor C2 is zero when the power source is activated, the upper potential of the capacitor C2 is 0V. After the power supply is activated, the constant current source 171a charges the capacitor C2 with a constant current, so that the potential of the capacitor C2 rises in proportion to time at a constant rate as shown in FIG. . When this voltage reaches Vref, it is maintained at a constant voltage (Vref) by the action of the clamp circuit 175 .

  FIG. 6 shows an example of the clamp circuit 175 shown in FIG. The clamp circuit 175 includes an operational amplifier 176 and a switching transistor 177. The potential Vcl on the upper side of the capacitor C2 is input to the non-inverting input (+) of the operational amplifier. The output of the operational amplifier 176 drives the switching transistor 177. The switching transistor 177 receives the output of the operational amplifier 176, controls the voltage output from the voltage source of the predetermined voltage Vref, and outputs it as the output voltage Vco. The output voltage Vco is fed back to the inverting input (−) of the operational amplifier 176.

  The clamp circuit 175 is controlled so that the output voltage of the soft start circuit 17a does not exceed Vref.

  The on-resistance of the second switch 14 is controlled by the output of the error amplifier 15, and the output voltage is controlled to be a target voltage.

FIG. 7 is a diagram showing the relationship between the output of the soft start circuit 17a and the output voltage Vo. As shown in FIG. 7, as the output of the soft start circuit 17a increases at a constant rate, the value of the non- inverting input of the error amplifier 15 changes at a constant rate. As a result, the output voltage Vo is controlled by the output of the error amplifier 15, and the negative potential increases at a constant rate. When the soft start circuit 17a becomes a constant voltage (Vref), the output voltage of the output voltage Vo is output as a predetermined negative voltage according to this voltage. By this feedback control, an inversion type charge pump having a soft start function can be realized. Further, it is possible to operate the feedback function of the circuit immediately after power is turned, it is possible to prevent a negative overshoot of the negative voltage output of the power supply startup, the circuit elements of the load which the negative voltage is output Damage can be prevented. Further, at the time of steady operation, the reference side (inverted) input of the error amplifier 15 is provided with the GND potential, and the non-inverted input is provided with an output obtained by dividing the output voltages Vo and Vref of the output terminal Vo. It is difficult to receive and fluctuations in output voltage can be prevented.

  FIG. 8 is a block circuit diagram showing a charge pump circuit adopting an inversion mode for outputting a negative voltage in the third embodiment of the present invention. In addition, the same code | symbol is attached | subjected to the same component as FIG. 1, and the description of an overlapping part is omitted.

  In the third embodiment, a soft start circuit 17b using a negative voltage output as a negative power supply uses the soft start output based on the negative voltage output as an input on the inverting side (reference side) of the error amplifier 15.

  That is, an output obtained by dividing the output voltage Vo of the output terminal Vo is given to the non-inverting input of the error amplifier 15, and the output of the soft start circuit 17b is given to the inverting input. The soft start circuit 17b drops at a constant rate from the reference voltage (Vref) level to a predetermined negative voltage level during the soft start period.

  FIG. 9 is a block circuit diagram showing an example of the soft start circuit of FIG. The soft start circuit 17b includes a constant current source 171b, a switch 174, a switching transistor 172, a clamp circuit 175b, and a capacitor C2. The capacitor C2 adjusts the soft start period and functions as a soft start adjustment period.

  In the soft start circuit 17b, the switch 174 is controlled so that the capacitor C2 is connected to the reference voltage source 173 side immediately after the power supply is started, and then the capacitor C2 is connected to the constant current source 171b. In the soft start circuit 17b, when the power supply is activated, the capacitor C2 is charged to the reference voltage Vref, so that the potential on the upper side of the capacitor C2 is Vref. After starting the power source, the negative power source is charged to the capacitor C2 to a negative voltage by the constant current source 171b, so that the potential of the capacitor C2 drops in proportion to time at a constant rate as shown in FIG. go. When this voltage reaches a constant negative voltage, the constant negative voltage is maintained by the action of the clamp circuit 175b.

  FIG. 10 is a diagram showing the relationship between the output of the soft start circuit 17b and the output voltage Vo. As shown in FIG. 10, as the output of the soft start circuit 17b decreases at a constant rate, the value of the inverting input of the error amplifier 15 changes at a constant rate. As a result, the output voltage Vo is controlled by the output of the error amplifier 15, and the negative potential increases at a constant rate. When the soft start circuit 17b becomes a constant negative voltage, the output voltage of the output voltage Vo is controlled to be a predetermined negative voltage according to this voltage.

  By this feedback control, an inversion type charge pump having a soft start function can be realized. In addition, it is possible to operate the feedback function in the circuit immediately after starting the power supply, to prevent negative overshoot of the negative voltage output at the time of power supply startup, and to prevent the negative voltage output circuit element on the load circuit side Can be prevented from being damaged. In a steady state, a negative voltage potential is applied to the reference side (inverted) input of the error amplifier 15, and an output obtained by dividing the output voltage Vo of the output terminal Vo is applied to the non-inverted input. It is difficult to prevent fluctuations in the output voltage.

  FIG. 11 is a block circuit diagram showing a charge pump circuit adopting an inversion mode for outputting a negative voltage in the fourth embodiment of the present invention. In addition, the same code | symbol is attached | subjected to FIG.1 and FIG.2 and an identical configuration part, and description of an overlapping part is omitted.

  As in the second embodiment, the fourth embodiment shown in FIG. 11 is configured to divide the output voltage Vo of the charge pump circuit and the output of the soft start circuit 17a and feed back the voltage.

The fourth embodiment is different from the second embodiment in that a P-type MOS transistor as the second switch means 14a is provided on the power supply side, and the first switch means 13 is provided on the ground side. Yes. Since the transistor as the second switch means is provided on the power supply side, the error amplifier 15 for supplying a control signal to the gate has the inverting input grounded (GND) and the non- inverting input connected to the output voltage Vo of the output terminal Vo. The divided output of the soft start circuit 17a is given. The soft start circuit 17a rises at a certain rate from the ground (GND) level to the reference voltage (Vref) level during the soft start period.

  The operation of the fourth embodiment shown in FIG. 11 is the same as that of the second embodiment.

  FIG. 12 is a block circuit diagram showing a charge pump circuit employing an inversion mode for outputting a negative voltage according to the fifth embodiment of the present invention. In addition, the same code | symbol is attached | subjected to FIG.1 and FIG.2 and an identical configuration part, and description of an overlapping part is omitted.

  In FIG. 12, the inverting charge pump circuit includes a voltage source VDD, an output capacitor 11, a flying capacitor 12, a first switch circuit 25 that connects the voltage source VDD and the flying capacitor 12 in parallel, and an output capacitor 11. And the second switch circuit 30 that connects the flying capacitor 12 in parallel, the drive circuit 40 that alternately turns on and off the first switch circuit 25 and the second switch circuit 30, and the first switch circuit 25 or the second switch circuit 25 And a control circuit 50 that controls the output voltage of the output capacitor 11 by adjusting the on-state impedance of the switch circuit 30. In the fifth embodiment, the control circuit 50 adjusts the on-state impedance of the second switch circuit 30.

  The drive circuit 40 includes an oscillation circuit 16 that generates a pulse signal having a predetermined frequency and an inverter 16a that inverts the oscillation output.

  The first switch circuit 25 includes a first switch 22 connected between the voltage source VDD and the positive side terminal of the flying capacitor 12, and a first switch connected between the ground potential and the negative side terminal of the flying capacitor 12. The rectifying means is composed of a switch 21. The second switch circuit 30 is connected between the second switch 32 connected between the ground potential and the positive terminal of the flying capacitor 12, and between the output capacitor 11 and the negative terminal of the flying capacitor 12. It is comprised from the switch 31 as a 2nd rectification | straightening means. The first and second switches 22 and 32 and the first and second rectifying elements 21 and 31 are configured by, for example, MOS transistors or the like. The first switch 22 and the first rectifier element 21 are turned on / off by the output of the oscillation circuit 16 of the drive circuit 40, and the second switch 32 and the second rectifier element 31 are inverters that invert the output of the oscillation circuit 16. Turns on and off by 16a.

  The control circuit 50 includes an error amplifier 15 that amplifies an error between the output voltage and a target value, a feedback resistor 19, a feedback resistor 20, and a soft start circuit 17a that generates a reference voltage.

  In the fifth embodiment, a soft start circuit 17 a is connected to the feedback resistor 20, and the output voltage of the soft start circuit 17 a and the output voltage (Vo) of the output voltage terminal Vo are divided by the feedback resistors 19 and 20.

  The non-inverting input of the error amplifier 15 is supplied with the output voltage Vo of the output terminal Vo and the output divided by the soft start circuit 17a, and the inverting input is supplied with ground (GND) as a reference voltage. The soft start circuit 17a rises at a constant rate from the ground (GND) level to the reference voltage (Vref) level during the soft start period.

  The control circuit 50 adjusts the resistance value when the first switch 25 is turned on or the resistance value when the second switch 30 is turned on. Alternatively, the on-resistance value of any one of the switches 21 and 22 in the first switch 25 and the on-resistance value of any of the switches 31 and 32 in the second switch 30 are adjusted.

  The operation of the inverting charge pump circuit configured as shown in FIG. 12 will be described below. First, the basic operation will be described.

  The DC voltage supplied from the voltage source VDD is supplied to the flying capacitor 12 through the first switch 22 and the first rectifying element 21 when the first switch 22 is turned on and the second switch 32 is turned off. Charged. Next, when the first switch 22 is turned off and the second switch 32 is turned on, the voltage charged in the flying capacitor 12 is inverted, and the output capacitor 11 is passed through the second switch 32 and the second rectifier 31. To generate a negative voltage.

  During the basic operation, a control signal is output from the control circuit 50 to the second rectifying element 31 of the second switch circuit 30, and the second rectifying element 31 receives the output of the control circuit 50 and has an on-resistance. Adjusted. By adjusting the on-resistance of the second switch circuit 30, the output voltage can be controlled and the output voltage can be kept constant. An inversion type charge pump is realized by this feedback control mechanism. Thus, the output voltage is controlled to be kept constant with respect to the fluctuation of the voltage source VDD and the fluctuation of the load current. Further, at the time of start-up, the soft start circuit 17a causes the voltage to rise from the GND level to the Vref level, so that overshoot or the like can be prevented. In a steady state, the reference potential (inverted) input of the error amplifier 15 is provided with the GND potential, and the non-inverted input is provided with an output obtained by dividing the output voltages Vo and Vref of the output terminal Vo. It is difficult to receive and fluctuations in output voltage can be prevented.

  The first switch 22 described above can be configured by a P-type MOS transistor, the second switch 32 can be configured by an N-type MOS transistor, and the first rectifier element 21 and the second rectifier element 31 can be configured by N-type MOS transistors.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description of the embodiments but by the scope of claims for patent, and is intended to include all modifications within the meaning and scope equivalent to the scope of claims for patent.

1 is a block circuit diagram showing a charge pump circuit adopting an inversion mode for outputting a negative voltage in a first embodiment of the present invention. FIG. FIG. 2 is a block circuit diagram showing an example of a soft start circuit in the circuit shown in FIG. 1. It is a figure which shows the relationship between the output of the soft start circuit in 1st Embodiment of this invention, and the output voltage Vo. It is the block circuit diagram which showed the charge pump circuit which employ | adopted the inversion mode which outputs the negative voltage in 2nd Embodiment of this invention. FIG. 5 is a block circuit diagram showing an example of a soft start circuit in the circuit shown in FIG. 4. FIG. 6 is a block circuit diagram showing an example of a clamp circuit in the soft start circuit shown in FIG. 5. It is a figure which shows the relationship between the output of the soft start circuit in 2nd Embodiment of this invention, and the output voltage Vo. It is the block circuit diagram which showed the charge pump circuit which employ | adopted the inversion mode which outputs the negative voltage in the 3rd Embodiment of this invention. FIG. 9 is a block circuit diagram illustrating an example of a soft start circuit in the circuit illustrated in FIG. 8. It is a figure which shows the relationship between the output of the soft start circuit in 3rd Embodiment of this invention, and the output voltage Vo. It is the block circuit diagram which showed the charge pump circuit which employ | adopted the inversion mode which outputs the negative voltage in 4th Embodiment of this invention. It is the block circuit diagram which showed the charge pump circuit which employ | adopted the inversion mode which outputs the negative voltage in the 5th Embodiment of this invention. It is a circuit diagram which shows the switching power supply using the switching regulator of the negative voltage output which has the conventional soft start function.

Explanation of symbols

11 output capacitor, 12 flying capacitor, 13 first switch means, 14 second switch means, 15 error amplifier, 16 oscillation circuit, 17 soft start circuit, 18 reference power supply, 19, 20 feedback resistor, VDD voltage source, GND ground.

Claims (4)

  A connection point between a voltage source, first and second rectifier elements connected in series between the ground and the output terminal, an output capacitor connected to the output terminal, and the first and second rectifier elements The first switching means having a switching capacitor that is alternately turned on and off, the second switching means connected to the first switching means, and the first switching means. An error amplifier for amplifying an error between the output voltage and a target value, comprising: a drive circuit; and a control circuit that controls an output voltage of the output capacitor by adjusting an on-resistance of the second switch means. The output voltage of the output terminal and the reference voltage are divided and given to the non-inverting side input of the error amplifier, the output of the soft start circuit is given to the inverting side input of the error amplifier, and the soft start The voltage inversion is characterized in that the output voltage of the output terminal is controlled to be output as a predetermined negative voltage when the output of the circuit drops at a constant rate from a reference voltage potential or a ground potential to a predetermined negative voltage potential. Type charge pump circuit.   The second switch means is an N-channel MOS transistor provided between the first switch means and ground, and supplies the output of the error amplifier to the gate of the N-channel MOS transistor. The voltage inversion type charge pump circuit according to claim 1. A connection point between a voltage source, first and second rectifier elements connected in series between the ground and the output terminal, an output capacitor connected to the output terminal, and the first and second rectifier elements The first switching means having a switching capacitor that is alternately turned on and off, the second switching means connected to the first switching means, and the first switching means. An error amplifier for amplifying an error between the output voltage and a target value, comprising: a drive circuit; and a control circuit that controls an output voltage of the output capacitor by adjusting an on-resistance of the second switch means. An output based on the soft start circuit is used for either the non-inverting side input or the inverting side input that is input to the error amplifier, and the output voltage of the soft start circuit and the output of the output terminal Voltage dividing means is further provided, and an output from the voltage dividing means is applied to either a non-inverting side input or an inverting side input to be input to the error amplifier, and the output of the soft start circuit is connected to ground. by increasing at a constant rate from the potential to the reference potential, the voltage inverting charge pump circuit, wherein the output voltage of the output terminal is output controlled as a predetermined negative voltage. The second switch means is an N-channel MOS transistor provided between the first switch means and ground, and provides an output of the voltage dividing means to a non-inverting side input of the error amplifier, 4. The voltage inversion type charge pump circuit according to claim 3, wherein an inversion side input is set to a ground potential and an output of the error amplifier is given to a gate of the N channel type MOS transistor.

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