JP2005312169A - Voltage-inverting charge pump circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stabilize an output voltage, in a voltage-inverting charge pump circuit. <P>SOLUTION: A voltage regulating circuit 10 detects the output voltage Vout, compares the output of voltage Vout with a reference voltage Vref, and feeds back the gate terminal of a voltage control element MOSFET 14 so as to satisfy the relation determined by resistors R1, R2. The MOSFET 14 is controlled at a voltage Vgs between its gate and its source by a gate voltage. A charge transfer speed between the charging capacitor C1 and an output capacitor C2 is controlled by changing a channel resistance so as to stabilize the output voltage Vout. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a voltage inverting charge pump circuit, and more particularly to a voltage inverting charge pump circuit having a regulation function for stabilizing an output voltage.

  In a small information terminal represented by a mobile phone, a PHS (Personal Handy Phone), a PDA (Personal Digital Assistance) and the like, there are many devices that require a negative power source in an internally used device. However, many small information terminal devices such as mobile phones use a Li-ion battery that outputs a positive voltage with an output voltage of about 3.2 to 4.2 V as a voltage source, and has a negative power source. Not done. Therefore, a negative voltage is generated by a voltage inversion type DC / DC converter to drive a device that requires the negative power source.

As a technique for generating such a negative voltage, as disclosed in Patent Document 1, a voltage inversion type charge pump circuit that repeats charge transfer between a charging capacitor and an output capacitor is widely used.
JP 2001-258241 A

  However, such a voltage inverting charge pump circuit may not be used as it is for applications requiring stable voltage supply because its output voltage varies depending on the state of the connected load and the input voltage. .

  The present invention has been made in view of these problems, and an object thereof is to provide a voltage inversion type charge pump circuit capable of generating a stable negative voltage without increasing the number of components.

  In one aspect of the present invention, a fixed voltage, that is, an input voltage higher than the ground potential is applied to one end of the capacitor and a fixed voltage is applied to the other end, a fixed potential is applied to one end and the other end is loaded. And an inversion type charge pump circuit that outputs a voltage lower than a fixed potential to a load by alternately repeating a second period connected to the power supply, and a fixed voltage power supply between the fixed voltage power supply and the one end A voltage control element is inserted between the other end, an input voltage power source and the one end, or between a load and the other end, and this element is controlled and applied to the load. A circuit for controlling the voltage is provided.

  According to this aspect, by controlling the voltage control element by feeding back the output voltage, the resistance value of the charging / discharging path can be changed, and the output voltage can be stabilized to a desired voltage.

  When a MOSFET (Metal Oxide Field Effect Effect Transistor) is used as a voltage control element, a constant current continues to flow when a parasitic bipolar transistor and a parasitic thyristor existing inside the device are turned on by external input and noise. Latch-up that causes device destruction becomes a problem. This latch-up is likely to occur when a high voltage or a negative voltage is input to the input / output terminals of the device, especially when there is a region that operates with a negative voltage in the circuit as in the present invention. Have Accordingly, by providing the voltage control element in a path that operates in a voltage range higher than the fixed voltage as in the above embodiment, the risk of MOSFET latch-up can be greatly reduced.

  Further, when the voltage control element is provided in the path connected to the capacitor in the second period, the load response is good in addition to the latch-up prevention when the MOSFET is used as the voltage control element. The output voltage can be stabilized.

  According to another aspect of the present invention, there is provided a first period in which an input voltage higher than a fixed voltage is applied to one end of a capacitor via a first switch and a fixed voltage is applied to the other end via a second switch; An inversion type in which a fixed potential is applied to the one end via a switch and a second period in which the other end is connected to a load via a fourth switch is alternately repeated to apply a voltage lower than the fixed potential to the load. The charge pump circuit is provided with a circuit for controlling the voltage applied to the load by controlling the degree of ON of any of the first switch to the fourth switch.

  According to this aspect, by feeding back the output voltage and controlling the resistance values of the first switch to the fourth switch, the resistance value of the charging / discharging path is changed, and the output voltage is stabilized to a desired voltage. Is possible. In particular, when the degree of ON of the third switch is controlled by a circuit for controlling the voltage, a regulation function with good responsiveness can be obtained and the output voltage can be stabilized.

  It should be noted that any combination of the above-described constituent elements and a representation of the present invention converted between a method, an apparatus, a system, etc. are also effective as an aspect of the present invention.

  The voltage inverting charge pump circuit according to the present invention can regulate fluctuations of connected load and input voltage by feedback, and can supply a stable negative output voltage.

  Before explaining the embodiment of the present invention, in order to stabilize the output voltage of the voltage inverting charge pump circuit, a regulator is connected in series to the output of the voltage inverting charge pump circuit as shown in FIG. Consider. Such a circuit configuration has the following problems. Usually, externally required external components include a charging capacitor C1 and an output capacitor C2 used in the charge pump circuit 42. However, when a regulator is connected in series to the output of the charge pump circuit, in many applications, in addition to the two capacitors, a new output smoothing capacitor C3 is often required. It is disadvantageous in terms.

  Such a problem becomes an important problem directly related to the product power especially in a small information terminal that requires space saving. Therefore, it is necessary to consider a voltage inversion type charge pump circuit that solves these problems. The two embodiments described below solve these secondary problems in addition to the problem of stabilizing the output voltage.

  A first embodiment of the present invention will be described with reference to FIG. The voltage inverting charge pump circuit 100 according to the first embodiment of the present invention includes a charging capacitor C1, an output capacitor C2, first to fourth switches SW1 to SW4, and a voltage regulation circuit 10. The first switch SW1 to the fourth switch SW4, the charging capacitor C1, and the output capacitor C2 constitute a so-called voltage inversion type charge pump circuit that inverts the polarity of the input voltage Vin and outputs it as Vout = −Vin. The first switch SW1 and the second switch SW2 are respectively connected to both ends of the charging capacitor C1, the first switch SW1 is connected to the input voltage side, the second switch SW2 is connected to the fixed voltage, and in this embodiment, the ground potential. Yes. When these switches are turned on, the voltage Vin is applied to both ends of the charging capacitor C1 to be charged. The third switch SW3 has one end connected to the first switch SW1 side of the charging capacitor C1 and the other end connected to the drain terminal of the MOSFET 14 that is a voltage control element of the voltage regulation circuit 10. The fourth switch is inserted between both capacitors in order to connect and disconnect the charging capacitor C1 and the output capacitor C2 by turning on and off.

  The voltage regulation circuit 10 is a circuit that stabilizes the output voltage Vout by comparing the output voltage Vout and the reference voltage Vref, and includes resistors R1 and R2, an operational amplifier 12, and an Nch MOSFET 14. The resistor R1 has one end input with the reference voltage Vref and the other end connected to the non-inverting input terminal of the operational amplifier 12. The resistor R2 has one end that receives the output voltage Vout and the other end that is connected to the non-inverting input terminal of the operational amplifier 12. The inverting input terminal of the operational amplifier 12 is grounded, and the output terminal of the operational amplifier 12 is connected to the gate terminal of the Nch MOSFET 14 which is a voltage control element. The MOSFET 14 is inserted between the third switch SW3 and the ground potential, and exists in the charge / discharge path of the output capacitor C2 when the third switch SW3 is turned on. Therefore, the MOSFET 14 can adjust the charge amount of the output capacitor C2 by controlling the gate voltage, and has a function of controlling the output voltage Vout as a result.

  The operation of the voltage inverting charge pump circuit 100 having the regulation function configured as described above will be described below. In the first period, the first switch SW1 and the second switch SW2 are turned on, and the third switch SW3 and the fourth switch SW4 are turned off. During this period, the charging capacitor C1 is charged to the input voltage Vin. On the other hand, the output capacitor C2 is disconnected from the charging capacitor C1 during this period, and when power is supplied to the load circuit 16, the output voltage Vout gradually rises from a desired voltage.

  Therefore, in the second period, the first switch SW1 and the second switch SW2 are turned off, and the third switch SW3 and the fourth switch SW4 are turned on. During this period, the charge stored in the charging capacitor C1 is transferred to the output capacitor C2 via the fourth switch SW4, and the output voltage Vout that has risen by supplying power to the load circuit 16 is changed to the desired output voltage again. Charge until

  By alternately repeating the first period and the second period, the voltage inversion type charge pump circuit can continuously supply charges to the output capacitor C2 and obtain a negative voltage as the output voltage Vout. If the load circuit 16 is constant and the input voltage Vin is also constant, it is possible to output a constant negative voltage in a steady state by repeating the first period and the second period. Changes, the output voltage Vout fluctuates.

  Therefore, the voltage regulation circuit 10 monitors the output voltage Vout and applies feedback to the gate terminal of the MOSFET 14 that is a voltage control element so that the following relationship is established with the reference voltage Vref.

(Equation 1)
Vout = −R2 / R1 × Vref
By applying feedback to the gate voltage of the MOSFET 14 which is a voltage control element, the gate-source voltage Vgs of the MOSFET 14 changes and the channel resistance is controlled. The channel resistance of the MOSFET 14 can control charge transfer between the charging capacitor C1 and the output capacitor C2 in the second period, and the output voltage Vout can always be stabilized to a desired voltage by feedback.

  Thus, according to the first embodiment, by providing the regulation function in the charge pump circuit, it is possible to obtain a stable output voltage without increasing the number of components outside. That is, the capacitor C3 required in the circuit shown in FIG. 3 can reduce the number of parts by one because the output capacitor C2 also plays a role in the first embodiment. In the charge pump circuit that outputs a negative voltage, attention must be paid to the latch-up of the MOSFET 14 used as the voltage control element. In the present embodiment, the potential between the third switch SW3 and the fixed voltage is used. Is always a positive voltage. Therefore, even when a device that is relatively weak in latch-up is used for the MOSFET 14 and the switch of the voltage control element, the possibility of latch-up is greatly reduced, which is particularly effective. Furthermore, by inserting the MOSFET 14 between the third switch SW3 and the fixed voltage, the switch on the discharge side is controlled, so that a fast load response can be obtained and the ripple and overshoot of the output voltage Vout are reduced. It becomes possible to do.

  In the present embodiment, the case where the MOSFET 14 which is a voltage control element is inserted between the third switch SW3 and the fixed voltage has been described. However, between the first switch SW1 and the charging capacitor C1, and between the first switch SW1 and the input terminal Vin. May be inserted. Even in this case, since the MOSFET 14 always operates at a positive voltage, the output voltage can be stabilized while reducing the possibility of latch-up. The MOSFET 14 may be inserted between the fourth switch SW4 and the charging capacitor C1, and between the fourth switch SW4 and the output capacitor C2, and at this time, the discharge path is controlled as in the first embodiment. Therefore, fast load response can be obtained. Further, the MOSFET 14 may be connected to any other switch, and the output voltage can be stabilized even when connected to any terminal of the second switch SW2 or between other switches.

  FIG. 2 is a circuit diagram of a voltage inversion type charge pump circuit according to the second embodiment of the present invention. The voltage inversion type charge pump circuit 300 according to the second embodiment is similar to the first embodiment in that the charge pump circuit itself has the regulation function, but the regulation method is different. . That is, in the second embodiment, the output voltage is stabilized not by controlling the resistance value of the charging / discharging path but by adjusting the degree of ON of the switch.

  The voltage inversion type charge pump circuit 300 according to the second embodiment also includes a charging capacitor C1, an output capacitor C2, first to fourth switches SW1, SW2, SW3, SW4, and a voltage regulation circuit 36. . In the second embodiment, the first switch SW1 is a Pch MOSFET, and the second switch SW2 to the fourth switch SW4 are Nch MOSFETs. The operation of the voltage inversion type charge pump circuit main body is not different from that of a normal charge pump circuit.

  The voltage regulation circuit 36 includes resistors R1 and R2, an operational amplifier 12, and an amplitude control circuit 32, and feedback is applied so that the output voltage Vout satisfies the above equation. The amplitude control circuit 32 has a function of outputting a clock signal having a voltage amplitude corresponding to the amplitude control signal AMP in synchronization with the input clock signal. An amplitude control signal AMP that is an output signal of the operational amplifier 12 is input to the amplitude control terminal of the amplitude control circuit 32, and the amplitude of the clock signal CLK from the oscillator 34 that is the input signal is changed to change the third amplitude control signal AMP. Input to the gate terminal of the switch SW3. The clock signal CLK is generated by the oscillator 34 and is synchronized with a clock signal for turning on and off other switches not shown in FIG.

  The gate-source voltage Vgs of the MOSFET is changed by the voltage input to the gate terminal of the third switch SW3, and the drain current Ids of the MOSFET is controlled. The drain current Ids is nothing but the charge transfer rate performed between the charging capacitor C1 and the output capacitor C2 via the fourth switch SW4 in the second period. As a result, the charge amount of the output capacitor, that is, the output voltage Vout can be controlled by the degree of ON of the third switch.

  As described above, according to the second embodiment, in the second period in which the third switch is turned on, the current in the charge / discharge path in the second period is controlled by adjusting the degree of the on-state, and the output voltage It is possible to provide a regulation function so that Vout becomes constant. Further, as in the first embodiment, no new parts are required outside.

  These embodiments are exemplifications, and it will be understood by those skilled in the art that various modifications can be made to combinations of the respective constituent elements and processing processes, and such modifications are within the scope of the present invention. is there.

  For example, in the second embodiment, the degree of ON of the switch is controlled by the gate-source voltage Vgs as in this embodiment, and the duty ratio of the clock signal applied to the gate terminal of the switch is changed. This can also be realized. In the second embodiment, the gate voltage of the third switch SW3 is controlled. Of course, the output voltage Vout is also stabilized by the gate voltages of the other first, second, and fourth switches. Can be planned.

1 is a circuit diagram showing a voltage inversion type charge pump circuit according to a first embodiment of the present invention. It is a circuit diagram which shows the voltage inversion type charge pump circuit based on the 2nd Embodiment of this invention. It is a circuit diagram which shows the voltage inversion type | mold charge pump circuit with a regulation function for understanding embodiment of this invention.

Explanation of symbols

  10 voltage regulation circuit, 12 operational amplifier, 14 MOSFET, 16 load circuit, 32 amplitude control circuit, 34 oscillator, 36 voltage regulation circuit, 100 voltage inversion type charge pump circuit, 300 voltage inversion type charge pump circuit, SW1 first switch, SW2 second switch, SW3 third switch, SW4 fourth switch, C1 charging capacitor, C2 output capacitor, R1 resistor, R2 resistor, CLK clock signal, AMP amplitude control signal.

Claims (5)

A first period in which an input voltage higher than a fixed voltage is applied to one end of the capacitor and the fixed voltage is applied to the other end; a second period in which the fixed potential is applied to the one end and the other end is connected to a load; Is an inversion type charge pump circuit that applies a voltage lower than the fixed potential to the load by alternately repeating
For voltage control between the fixed voltage power source and the one end, between the fixed voltage power source and the other end, between the input voltage power source and the one end, or between the load and the other end. And a circuit for controlling the voltage to be applied to the load by controlling the element.   The charge pump circuit according to claim 1, wherein the element is provided in a path that operates in a voltage range higher than the fixed voltage.   The charge pump circuit according to claim 1, wherein the element is provided in a path connected to the capacitor in the second period. A first period in which an input voltage higher than a fixed voltage is applied to one end of the capacitor via the first switch and the fixed voltage is applied to the other end via the second switch, and the one end to the one end via the third switch An inverting charge pump circuit for applying a voltage lower than the fixed potential to the load by alternately applying a fixed potential and a second period in which the other end is connected to the load via a fourth switch. Because
A charge pump circuit comprising a circuit for controlling a voltage applied to the load by controlling a degree of ON of any one of the first switch to the fourth switch.   5. The charge pump circuit according to claim 4, wherein the circuit for controlling the voltage controls the degree of ON of the third switch.

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