JP4848692B2 - Boost power supply circuit and boost method - Google Patents

Description

  The present invention relates to a boost power supply circuit and a boost method.

FIG. 15 is a block diagram showing a conventional example of a boost power supply circuit, and FIG. 16 is a timing chart of the boost power supply circuit shown in FIG.
The boosting power supply circuit shown in FIG. 15 includes a charge pump circuit 1-1, an error amplifier 120, a starting current control circuit 110, and an overcurrent limiting circuit 5.

  The starting current control circuit 110 gradually increases the reference voltage source 7 that generates the reference voltage and the reference voltage from the reference voltage source 7 at a predetermined rate of increase (for example, several hundred μs from 0 V to the rated voltage). It comprises a known soft start circuit 8 that prevents the occurrence of an excessive input inrush current. The error amplifier 120 has feedback resistors R1 and R2 that divide the output voltage of the charge pump circuit 1, the output voltage from the soft start circuit 8 applied to one input terminal, and the feedback resistors R1 and R2 connected to the other input terminal. A differential input circuit 3 to which a voltage from a branch point is applied; an NchMOS transistor (hereinafter referred to as “transistor”) M6 whose gate is connected to an output terminal of the differential input circuit 3 and whose source is grounded; A capacitor C5 connected between the gate and the drain, PchMOS transistors (hereinafter referred to as “transistors”) M3 to M5 whose gate is connected to the drain of the transistor M6 and whose source is connected to the input line, and both ends of the transistor M5 Current source FI and a drain connected between the drain of transistor M3 and the drain of transistor M2. A pitch SW8, the drain is connected to the switch SW8, and is constituted by the transistor M2 whose sources are grounded.

  The charge pump circuit 1-1 includes a capacitor C1, a switch SW1 connected between one end (right end in the drawing) of the capacitor C1 and an input, a switch SW4 connected between one end of the capacitor C1 and an output, and a capacitor The switch SW3 connected between the other end (the left end in this case) of C1 and the input, the other end of the capacitor C1 and the drain are connected, the source is grounded, and the transistor M1 is connected between the gate and the ground. The switch SW2 and a capacitor C2 connected between the output and the ground.

  Each switch SW1 to SW4 is turned on (1 logic level) and turned off (0 logic level) in accordance with the output signal of the clock control circuit 2, and is realized by a known transistor circuit.

As shown in FIG. 16, the clock control circuit 2 controls the switches SW1 to SW4 and SW8 and the transistors M1 and M2 of the charge pump circuit 1-1.
The phases of ON and OFF of the switches SW1 and SW8 are opposite to the phases of the other switches SW2, SW3 and SW4, and the transistor M1 is turned on and off in response to the ON and OFF of the switch SW1. It has become. Further, SW1 and SW8 and the other SW2, SW3 and SW4 have an OFF section to prevent a through current due to simultaneous ON.

The capacitor C5 and the transistor M6 constitute a phase compensation circuit for preventing the differential input circuit 3 from oscillating. Similarly, the capacitor C6 and the transistor M7 also have a phase for preventing the differential input circuit 10 from oscillating. A compensation circuit is configured.
As a result, the boosting power supply circuit shown in FIG. 15 has the characteristics shown in FIG.
FIG. 19 is a characteristic diagram of the boosting power supply circuit shown in FIG.
In FIG. 19, the horizontal axis is the input current axis, and the vertical axis is the output voltage axis.

Even if the output terminal of the charge pump circuit section is short-circuited to the ground voltage, it has an overcurrent protection circuit that can reduce the current output from the charge pump circuit section to a desired current value, and is equipped with a constant voltage circuit in the previous stage A charge pump type DC-DC converter (see, for example, Patent Document 1) is disclosed.
JP 2004-320862 A

17 and 18 are diagrams showing current paths in the respective states of the boost power supply circuit shown in FIG.
As the output current is pulled (increased), the overcurrent limit is applied and the voltage drops rapidly. When the output voltage becomes lower than the input voltage, the overcurrent limiting circuit 5 (see FIG. 15) operates in the current path shown in FIG. 17 to limit the gate voltage of the transistor M1, but in the current path shown in FIG. M1 is not involved, and the current limiting function does not work at all. When the output is short-circuited, the capacitor C1 is fully charged again, so that a large current flows from the input.

  That is, when the output is short-circuited, the ON resistance of the transistor M1 increases by the AMP (Amplifier) feedback control in the current path shown in FIG. 17, and the charging current to the capacitor C1 can be controlled. In the current path shown, since the output is 0 V, the charge is lost and the charging current flows again. Moreover, since the AMP feedback control does not function, a large current flows to the capacitor C1 to the full capacity of the switches SW3 and SW4.

  The technique described in Patent Document 1 relates to an output stabilization method in which a charge pump operation is turned ON / OFF to obtain a constant output voltage. Since the oscillation circuit repeats operation → stop, it is not suitable for a large current load in consideration of the oscillation stabilization time. The load current-output voltage characteristics at high voltage and large current are insufficient.

  In the technology described in Patent Document 1, there is a regulator circuit in the previous stage of the charge pump circuit, and a charge pump output monitor is added to limit the current in the output transistor on the regulator side. Not suitable for large current output.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a boosting power supply circuit and a boosting method capable of obtaining a stable output voltage even with a high voltage and a large current with little power loss.

In order to solve the above-mentioned problem, an invention according to claim 1 is characterized in that an error amplifier that performs negative feedback through a resistor, an overcurrent limiting circuit that limits overcurrent, and a capacitance that is a charging path of the charge pump circuit and GND. In a boost power supply circuit that obtains a fixed output by controlling an input current of the charge pump circuit by controlling a gate voltage of a transistor provided therebetween, a comparator for comparing an input voltage and an output voltage, And a clock control circuit for controlling a starting current of the charge pump circuit in accordance with an output.

According to the first aspect of the present invention, a comparator for detecting the relationship between the input voltage and the output voltage and a clock control circuit for controlling the starting current of the charge pump circuit according to the output of the comparator are provided. As a result, since the relationship between the input and output voltages is reflected in the control of the charge pump circuit, the overcurrent can be limited to the input and output currents.

According to a second aspect of the present invention, there is provided an error amplifier to which negative feedback is applied via a resistor and an overcurrent limiting circuit for limiting an overcurrent, and a gate of a transistor provided between a capacitor and GND which is a charge path of a charge pump circuit. In a step-up power supply circuit that obtains a fixed output by controlling the input current of the charge pump circuit by controlling the voltage, the starting current control circuit includes an oscillation circuit that oscillates at a predetermined frequency, and an oscillation frequency of the oscillation circuit A clock control circuit that generates a clock pulse, and compares the input voltage with the output voltage of the charge pump circuit, and controls the charge pump circuit drive by the clock control circuit when the input voltage becomes lower than the output voltage. And a comparator for limiting overcurrent by changing a current path.

According to the second aspect of the present invention, the input voltage and the output voltage are compared, and when the input voltage becomes lower than the output voltage, the drive of the charge pump circuit is controlled by the clock control circuit to change the current path. By providing the comparator for limiting, the relationship between the input and output voltages is reflected in the control of the charge pump circuit, so that the overcurrent can be limited to the input and output current.

According to a third aspect of the present invention, there is provided a transistor provided between a capacitor and GND that is a charge path of a charge pump circuit by limiting an overcurrent by an error amplifier to which negative feedback is applied via a resistor and an overcurrent limiting circuit. In the boosting method for controlling the input current of the charge pump circuit by controlling the gate voltage and obtaining a fixed output, the comparator compares the input voltage with the output voltage, and the clock pulse control circuit outputs the output of the comparator. The starting current of the charge pump circuit is controlled according to the above.

According to the third aspect of the present invention, the input voltage and the output voltage are compared by the comparator, and the starting current of the charge pump circuit is controlled by the clock control circuit according to the output of the comparator. Since the relationship is reflected in the control of the charge pump circuit, the overcurrent can be limited to the input / output current.

According to a fourth aspect of the present invention, there is provided a transistor provided between a capacitor and GND, which is a charge path of a charge pump circuit by limiting an overcurrent by an error amplifier to which negative feedback is applied via a resistor and an overcurrent limiting circuit. In the step-up method for controlling the input current of the charge pump circuit by controlling the gate voltage and obtaining a fixed output, the oscillation circuit oscillates at a predetermined frequency, and the clock control circuit generates a clock based on the oscillation frequency of the oscillation circuit. A pulse is generated, an input voltage is compared with an output voltage of the charge pump circuit by a comparator, and when the input voltage becomes lower than the input voltage, driving of the charge pump circuit is controlled by the clock control circuit to It is characterized in that overcurrent is limited by changing.

According to the fourth aspect of the present invention, the input voltage and the output voltage are compared by the comparator, and when the input voltage becomes lower than the output voltage, the clock current of the clock control circuit is decreased to reduce the current consumption of the load. Since the relationship between the input and output voltages is reflected in the control of the charge pump circuit, a more stable output voltage can be obtained even at a high voltage and a large current.

  According to the present invention, it has an overcurrent limiting circuit that limits overcurrent and a starting current control circuit that controls the starting current of the charge pump circuit, and suppresses the input current when the output is short-circuited. A stable output voltage can be obtained even at high voltage and large current without using a regulator.

Embodiments of the boosting power supply circuit according to the present invention include an overcurrent limiting circuit for limiting an overcurrent and a starting current control circuit for controlling the starting current of the charge pump circuit in a boosting power supply circuit having an AMP feedback type charge pump circuit. has the door, it is assumed that so as to suppress the input current when the output is short-circuited.

  The charge pump circuit includes a plurality of capacitors, a plurality of switches for boosting the charge input to the capacitor at the previous stage by moving the charge to the capacitor at the subsequent stage, a feedback resistor for detecting the output voltage, the input voltage and the output A comparator having a comparator for comparing and amplifying the voltage and a clock control circuit for controlling ON / OFF of each switch based on an output signal of the comparator is used.

  The overcurrent limiting circuit performs current-voltage conversion by a resistor with respect to the current flowing through the gate of the switching transistor used in the charge pump circuit, and uses the voltage as a reference voltage for the error amplifier of the AMP feedback charge pump circuit. What is used is used.

  As the starting current control circuit, a circuit that compares an output voltage with an input voltage and controls charging / discharging of the charge pump circuit according to the result is used.

One embodiment of the boosting power source circuit of the present invention, between the capacitor and the GND is a charge path of the charge pump circuit with the overcurrent limiting circuit for limiting the error amplifier and the overcurrent multiplied by the negative feedback via a resistor In a step-up power supply circuit that obtains a fixed output by controlling the input current of the charge pump circuit by controlling the gate voltage of the provided transistor, a comparator that compares the input voltage and the output voltage, and according to the output of the comparator And a clock control circuit for controlling the starting current of the charge pump circuit.

  As the transistor, an Nch MOS transistor and a Pch MOS transistor are used, but the present invention is not limited to this, and a bipolar transistor may be used.

  In another embodiment of the boosting power supply circuit according to the present invention, an error amplifier to which negative feedback is applied via a resistor and an overcurrent limiting circuit that limits overcurrent are provided between a capacitor that is a charging path of the charge pump circuit and GND. In the step-up power supply circuit that obtains a fixed output by controlling the input current of the charge pump circuit by controlling the gate voltage of the transistor provided in the circuit, the starting current control circuit includes an oscillation circuit that oscillates at a predetermined frequency, The clock control circuit that generates a clock pulse based on the oscillation frequency is compared with the input voltage and the output voltage of the charge pump circuit. When the input voltage becomes lower than the output voltage, the clock control circuit controls the driving of the charge pump circuit. And a comparator for limiting overcurrent by changing the current path.

  As the oscillation circuit, a crystal oscillation circuit is preferable because it has excellent frequency characteristics. However, the present invention is not limited to this, and a PLL (Phase-Locked Loop) oscillation circuit, a Hartley oscillation circuit, a Colpitts oscillation circuit, a Vienna -Either a bridge oscillation circuit or a phase shift oscillation circuit may be used.

  As the clock control circuit, a plurality of latches configured to take the AND of two input signals and turn on / off each switch are used.

A comparator is used as the comparison circuit.
For example, a band gap reference circuit is used as the reference voltage source, but a constant voltage source such as a Zener diode may be used.

An embodiment according to the boosting method of the present invention is a boosting method for boosting an input voltage using an AMP feedback type charge pump circuit, in which an overcurrent is limited by an overcurrent limiting circuit, and an activation current control circuit is used for the charge pump circuit. It is assumed that the input current when the output is short-circuited is controlled by controlling the starting current.

  According to another embodiment of the boosting method of the present invention, an error amplifier to which negative feedback is applied via a resistor and an overcurrent limiting circuit limit the overcurrent, and the capacitance between the capacitor and GND, which is a charge path of the charge pump circuit. In the boosting method of obtaining a fixed output by controlling the input current of the charge pump circuit by controlling the gate voltage of the transistor provided in the starting current control circuit, the starting current control circuit compares the input voltage and the output voltage by a comparator, The pulse control circuit controls the start-up current of the charge pump circuit according to the output of the comparator.

According to another embodiment of the boosting method of the present invention, an error amplifier to which negative feedback is applied via a resistor and an overcurrent limiting circuit limit the overcurrent, and the capacitance between the capacitor and GND, which is a charge path of the charge pump circuit. In the boosting method of controlling the input voltage of the charge pump circuit by controlling the gate voltage of the transistor provided in the circuit and obtaining a fixed output, the oscillation circuit oscillates at a predetermined frequency and the clock control circuit sets the oscillation frequency of the oscillation circuit. A clock pulse is generated based on the input voltage, and the comparator compares the input voltage with the output voltage of the charge pump circuit. When the input voltage becomes lower than the output voltage, the clock control circuit controls the drive of the charge pump circuit to control the current path. It is characterized by limiting the overcurrent by changing.

〔Constitution〕
FIG. 1 is a block diagram showing an embodiment of a boosting power supply circuit to which the boosting method of the present invention is applied.
The boosting power supply circuit shown in FIG. 1 includes a charge pump circuit 1-1, an overcurrent limiting circuit 5, and a starting current control circuit 11.

  The starting current control circuit 11 includes a reference voltage source 7 that generates a reference voltage, and a soft start that gradually increases the reference voltage from the reference voltage source 7 at a predetermined rate of increase (for example, several hundred μs from 0 V to the rated voltage). The circuit 8, the comparator 9, and the clock control circuit 2 are included. The error amplifier 120 has feedback resistors R1 and R2 that divide the output voltage of the charge pump circuit 1, the output voltage from the soft start circuit 8 applied to one input terminal, and the feedback resistors R1 and R2 connected to the other input terminal. A differential input circuit 3 to which a voltage from a branch point is applied, a transistor M6 whose gate is connected to the output terminal of the differential input circuit 3 and whose source is grounded, and a capacitor connected between the gate and drain of the transistor M6 C5, a transistor M6 whose gate is connected to the output terminal of the differential input circuit 3 and whose source is grounded, a capacitor C5 connected between the gate and the drain of the transistor M6, and a gate whose source is connected to the drain of the transistor M6 Transistors M3 to M5 connected in common, a current source FI connected to both ends of the transistor M5, and a drain of the transistor M3 Composed of the connected switch SW8.

  The overcurrent limiting circuit 5 has a differential input circuit 10 with one input (upper side in the figure) connected to the branch point of the feedback resistors R1 and R2, and a gate connected to the output terminal of the differential input circuit 10 and a source. The grounded transistor M7, the capacitor C6 connected between the drain and gate of the transistor M7, and one end (the upper side in the figure) are connected to the other input (the lower side in this case) and the other end (the lower side in this case) In this case, the lower side is composed of a grounded resistor R3 and a capacitor C4 connected in parallel to the resistor R3.

  The charge pump circuit 1-1 has a switch SW1 connected between one end (right side in the figure) of the capacitor C1 and the input, SW3 connected between the other end (left side in the figure) and the input of the capacitor C1, and a drain having a capacitance. The transistor M1 connected to the other end of C1 (left side in the figure) and grounded at the source, the switch SW2 connected between the gate and the source of the transistor M1, and one end (lower end in the figure) of the capacitor C1 are grounded and the other end (In this case, the upper end) is composed of a capacitor C2 connected to one end (right side in the figure) of the capacitor C1.

[Operation]
First, the comparator 9 compares the input voltage with the output voltage.
When the input voltage is lower than the output voltage, the clock control circuit 2 operates the switches SW1 to SW4 and SW8 and the transistors M1 and M2 in the charge pump circuit 1-1 as shown in FIG.

Here, FIG. 2 is a diagram showing a timing chart of the boosting power supply circuit shown in FIG.
In FIG. 2, each horizontal axis represents a time axis, the upper stage represents a switch SW1, the next stage represents a switch SW2, the gate voltages of transistors M1 and M2, and the logical level axes of switches SW3, SW4, and SW8.

3 and 4 show current paths during operation of the booster power supply circuit shown in FIG.
In the current path state shown in FIG. 3 (switches SW1 and SW8 are ON, and switches SW2 to SW4 are OFF), the gate voltage is controlled so that the transistors M1 and M2 are turned on by the error amplifier 120 (see FIG. 1). Thus, the charging current to the capacitor C1 is controlled. That is, the current path is switch SW1 → capacitance C1 → transistor M1 → ground.

On the other hand, in the current path state shown in FIG. 4 (switches SW1 and SW8 are OFF and switches SW2 to SW4 are ON), the charge controlled by the capacitor C1 is charged to the capacitor C2. That is, the current path is switch SW3 → capacitance C1 → switch SW4 → capacitance C2.
As a result, an output voltage having an arbitrary value set by the voltage at the branch point of the feedback resistors R1 and R2 and the voltage of the reference voltage source 7 is obtained.

  In the step-up power supply circuit shown in FIG. 1, when the output current continues to be drawn (continues to flow) and reaches a certain output current value, the overcurrent limiting circuit 5 connected to the subsequent stage of the error amplifier 120 causes the charge pump circuit 1-1 to The gate voltages of the transistors M1 and M2 are limited, and the charging current of the capacitor C1 is limited. As a result, the output voltage decreases.

The overcurrent limiting circuit 5 performs current-voltage conversion by flowing a current proportional to the transistor M1 through the resistor R3. Output feedback is used as a reference for the differential input circuit 10. When a current exceeding the set value is detected, the transistor M7 of the overcurrent limiting circuit 5 functions to throttle the gate of the transistor M6 and reduce the capability of the transistor M1.
That is, when current-voltage conversion is performed by flowing a current proportional to the transistor M1 through a resistor, if the converted voltage value is higher than the voltage divided by the feedback resistors R1 and R2, the transistor of the overcurrent limiting circuit 5 Lower the gate voltage of M7. Then, the drain potential of the transistor M7 increases, the current value of the current mirror circuit CM1 decreases, and the current of the current mirror circuit CM2 also decreases. As a result, the current value of the transistor M1 decreases. When the current value of the transistor M1 decreases, the current is limited.
The reason for taking the input of the differential input circuit 10 from the output feedback side is to more strongly limit the overcurrent as the output decreases.

  If the output current is further pulled, the input voltage becomes higher than the output voltage. When the comparator 9 detects that the input voltage is higher than the output voltage, the clock control circuit 2 operates the charge pump circuit 1-1 as shown in the timing chart of FIG.

FIG. 5 is a timing chart of the boost power supply circuit shown in FIG.
In FIG. 5, each horizontal axis represents a time axis, the upper stage is a switch SW1, the next stage is a switch SW2, the gate voltages of transistors M1 and M2, and the logical level axes of switches SW3, SW4 and SW8.

By always performing ON voltage control of the transistors M1 and M2 by the error amplifying circuit 3 shown in FIG. 1 and constantly turning off the switch SW3, the operation of the overcurrent control circuit 5 is always effective, and input and output current control is performed. It becomes possible. When the input voltage becomes higher than the output voltage, current paths as shown in FIGS. 3 and 6 are alternately repeated at an optimal interval.
FIG. 6 is a diagram showing a current path of the boost power supply circuit shown in FIG.

  That is, when the input voltage becomes higher than the output voltage, first, the switches SW1 and SW8 are turned on and the switches SW2 to SW4 are turned off, so that the current path is as follows: switch SW1 → capacitance C1 → transistor M1 → ground. (FIG. 3).

  Next, after a predetermined time elapses, the switches SW1 to SW3 are turned off and the switches SW4 and SW8 are turned on, so that the current path becomes transistor M1 → capacitance C1 → switch SW4 → capacitance C2 (FIG. 6).

As a result of the drive control of the charge pump circuit 1-1 described above, the characteristics shown in FIG. 7 can be obtained.
FIG. 7 is a characteristic diagram of the step-up power supply circuit shown in FIG. 1, in which the horizontal axis represents the input current axis and the vertical axis represents the output voltage axis.
When the drive control of the charge pump circuit 1-1 is changed when the output voltage becomes lower than the input voltage, the boosting rate can be lowered to greatly reduce the power consumption of the load, and the input current when the output is short-circuited is also greatly increased. Can be suppressed. For this reason, this step-up power supply circuit can protect a circuit serving as a load from heat generation and destruction due to overcurrent.
Further, since the control shown in FIG. 5 is also performed when the charge pump circuit 1-1 is started, the start-up current can be controlled, and a soft start design is possible.

Next, another embodiment of the booster power supply circuit of the present invention will be described.
FIG. 8 is a block diagram showing another embodiment of the boost power supply circuit of the present invention.
〔Constitution〕
In this embodiment, the case of a 1.5 × booster circuit will be described.
The difference between the boosting power supply circuit shown in FIG. 8 and the boosting power supply circuit shown in FIG. 1 is that the charge pump circuit is different.
The boosting power supply circuit shown in FIG. 8 includes a charge pump circuit 1-2, an overcurrent limiting circuit 5, and a starting current control circuit 11.

  The starting current control circuit 11 includes a reference voltage source 7 that generates a reference voltage, and a soft start that gradually increases the reference voltage from the reference voltage source 7 at a predetermined rate of increase (for example, several hundred μs from 0 V to the rated voltage). The circuit 8, the comparator 9, and the clock control circuit 2 are included. The error amplifier 120 has feedback resistors R1 and R2 that divide the output voltage of the charge pump circuit 1, the output voltage from the soft start circuit 8 applied to one input terminal, and the feedback resistors R1 and R2 connected to the other input terminal. A differential input circuit 3 to which a voltage from a branch point is applied, a transistor M6 whose gate is connected to the output terminal of the differential input circuit 3 and whose source is grounded, and a capacitor connected between the gate and drain of the transistor M6 C5, a transistor M6 whose gate is connected to the output terminal of the differential input circuit 3 and whose source is grounded, a capacitor C5 connected between the gate and the drain of the transistor M6, and a gate whose source is connected to the drain of the transistor M6 Transistors M3 to M5 connected in common, a current source FI connected to both ends of the transistor M5, and a drain of the transistor M3 Composed of the connected switch SW8.

  The overcurrent limiting circuit 5 has a differential input circuit 10 with one input (upper side in the figure) connected to the branch point of the feedback resistors R1 and R2, and a gate connected to the output terminal of the differential input circuit 10 and a source. The grounded transistor M7, the capacitor C6 connected between the drain and gate of the transistor M7, and one end (the upper side in the figure) are connected to the other input (the lower side in this case) and the other end (the lower side in this case) In this case, the lower side is composed of a grounded resistor R3 and a capacitor C4 connected in parallel to the resistor R3.

  The charge pump circuit 1-2 has a capacitor C1, a switch SW4 connected between one end (right end in the figure) and the output of the capacitor C1, one end (upper end in the figure) connected to the switch SW4, and the other end (this In this case, the capacitor C2 whose lower end is grounded, the switch SW7 whose one end (left end in the figure) is connected to one end of the capacitor C1, the capacitor C3 whose one end (left end in the figure) is connected to the switch SW7, and the capacitor C3 A switch SW5 connected between one end (the left end in the figure) and the input, a switch SW3 connected between the other end (the left end in this case) and the input of the capacitor C1, and the other end of the capacitor C3 (in this case) Switch SW1 connected between the right end) and the input, switch SW6 connected between the other end of the capacitor C3 and the output, and a transistor M1 whose drain is connected to the other end of the capacitor C1 and whose source is grounded. And the tiger Is composed of a gate of the registers M1 and switch SW2 connected between the ground and the switch SW1, SW3, SW5 is turned ON, one end to the output voltage of the capacitor C2 is adapted to generate.

[Operation]
First, the comparator 9 compares the input voltage with the output voltage.
When the input voltage is lower than the output voltage, the clock control circuit 2 operates SW1 to SW8 in the charge pump circuit 1 and the transistors M1 and M2 as shown in FIG.

Here, FIG. 9 is a timing chart of the step-up power supply circuit shown in FIG.
In FIG. 9, each horizontal axis represents a time axis, the upper stage represents the switch SW1, the next stage represents the switch SW2, the gate voltages of the transistors M1 and M2, and the logic level axes of the switches SW3 to SW8.

10 and 11 are diagrams showing current paths of the boost power supply circuit shown in FIG.
In the current path state shown in FIG. 10 (switches SW1, SW7, SW8 are ON and switches SW2-6 are OFF), the voltage is controlled by error amplifier 120 (see FIG. 8) so that transistor M1 is turned ON. The charging current to the capacitor C1 and the capacitor C2 is controlled. That is, the current flows in the order of the switch SW1, the capacitor C3, the switch SW7, the capacitor C1, the transistor M1, and the ground.

In the state of the current path shown in FIG. 11 (switches SW1, SW7, SW8 are OFF and switches SW2-6 are ON), the charge controlled to be charged in the capacitors C1 and C3 is charged in the capacitor C2. As a result, an arbitrary output voltage set by the voltage at the branch point of the feedback resistors R1 and R2 and the voltage of the reference voltage source 7 is obtained.
When the output current continues to be reached and reaches a certain output current value, the overcurrent limiting circuit 5 connected to the subsequent stage of the error amplifier 120 (see FIG. 8) sets the gate voltages of the transistors M1 and M2 in the charge pump circuit 1-2. Limitation is applied and the charging currents of the capacitors C1 and C3 are limited. As a result, the output voltage decreases.

If the output current is further pulled in such a state, the input voltage becomes higher than the output voltage. When the comparator 9 detects that the input voltage is higher than the output voltage, the clock control circuit 2 operates the charge pump circuit 1-2 as shown in the timing chart of FIG.
FIG. 12 is a timing chart of the boosting power supply circuit shown in FIG.
The operation of the overcurrent control circuit 5 is always effective by always performing ON voltage control of the transistors M1 and M2 by the error amplifier 120, always turning off the switches SW3, SW4, and SW5, and always turning on the switch SW7. Thus, input and output current control becomes possible. The current path when the input voltage becomes higher than the output voltage is shown in FIGS.

  In the current path state shown in FIG. 10 (switches SW1, SW7, SW8 are ON, and switches SW2-SW6 are OFF), the charging currents to the capacitors C1, C3 are controlled. That is, the current path is as follows: switch SW1 → capacitance C3 → switch SW7 → capacitance C1 → transistor M1 → ground.

  In the state of the current path shown in FIG. 13 (switches SW1, SW6 to SW8 are ON, and switches SW2 to SW5 are OFF), the charges charged in the capacitors C1 and C3 are charged into the capacitor C2. That is, the current path is as follows: transistor M1 → capacitance C1 → switch SW7 → capacitance C3 → switch SW6 → capacitance C2.

As a result of the drive control of the charge pump circuit 1-2 described above, the characteristics shown in FIG. 14 can be obtained.
FIG. 14 is a characteristic diagram of the step-up power supply circuit shown in FIG. 8. The horizontal axis indicates the input current axis, and the vertical axis indicates the output voltage axis.
When the output voltage becomes lower than the input voltage, the drive control of the charge pump circuit 1-2 is changed, so that the step-up rate can be lowered and the power consumption of the load can be greatly reduced, and the input current when the output is short-circuited is greatly suppressed. it can. As a result, the load circuit can be protected from heat generation and destruction due to overcurrent.
Further, since the charge pump circuit 1-2 is activated at the same time as the control shown in FIG. 5, the activation current can also be controlled, and a soft start design is possible.

  Since the present invention is a step-up power supply circuit, it can be used in general industries such as a memory power supply, an electronic device using the memory, a manufacturing apparatus using the electronic device, a mechanical product, an automobile, a ship, and an aircraft.

It is a block diagram which shows one Example of the pressure | voltage rise power supply circuit to which the pressure | voltage rise method of this invention is applied. FIG. 2 is a diagram showing a timing chart of the boost power supply circuit shown in FIG. 1. FIG. 2 is a diagram showing a current path during operation of the boost power supply circuit shown in FIG. 1. FIG. 2 is a diagram showing a current path during operation of the boost power supply circuit shown in FIG. 1. FIG. 2 is a diagram showing a timing chart of the boost power supply circuit shown in FIG. 1. FIG. 2 is a diagram showing a current path of the boost power supply circuit shown in FIG. 1. FIG. 2 is a characteristic diagram of the boost power supply circuit shown in FIG. 1. It is a block diagram which shows the other Example of the step-up power supply circuit of this invention. FIG. 9 is a timing chart of the boost power supply circuit shown in FIG. 8. FIG. 9 is a diagram showing a current path of the boost power supply circuit shown in FIG. 8. FIG. 9 is a diagram showing a current path of the boost power supply circuit shown in FIG. 8. FIG. 9 is a timing chart of the boost power supply circuit shown in FIG. 8. FIG. 9 is a diagram showing a current path of the boost power supply circuit shown in FIG. 8. FIG. 9 is a characteristic diagram of the boost power supply circuit shown in FIG. 8. It is a block diagram which shows the prior art example of a step-up power supply circuit. 16 is a timing chart of the boost power supply circuit shown in FIG. FIG. 16 is a diagram showing a current path in each state of the boost power supply circuit shown in FIG. 15. FIG. 16 is a diagram showing a current path in each state of the boost power supply circuit shown in FIG. 15. FIG. 16 is a characteristic diagram of the boost power supply circuit shown in FIG. 15.

Explanation of symbols

1-1, 1-2 Charge pump circuit 2 Clock control circuit 3, 10 Differential input circuit 5 Overcurrent limiting circuit 6 Oscillation circuit 7 Reference voltage source 8 Soft start circuit 9 Comparator 11, 110 Start-up current control circuit 120 Error amplifier C1-C6 Capacitance M1, M2, M6, M7 NchMOS transistor (transistor)
M3-M5 PchMOS transistor (transistor)
R1-R3 resistance SW1-SW8 switch

Claims (4)

The charge amplifier is controlled by controlling the gate voltage of a transistor provided between a capacitor and GND, which is a charge path of a charge pump circuit, by an error amplifier that performs negative feedback through a resistor and an overcurrent limiting circuit that limits overcurrent. In a boost power supply circuit that obtains a fixed output by controlling the input current of the pump circuit,
A comparator that compares the input voltage with the output voltage;
A boosting power supply circuit comprising a starting current limiting circuit including a clock control circuit for controlling a starting current of the charge pump circuit in accordance with an output of the comparator. The charge amplifier is controlled by controlling the gate voltage of a transistor provided between a capacitor and GND, which is a charge path of a charge pump circuit, by an error amplifier that performs negative feedback through a resistor and an overcurrent limiting circuit that limits overcurrent. In a boost power supply circuit that obtains a fixed output by having a starting current control circuit that controls an input current of a pump circuit and an overcurrent limiting circuit that limits overcurrent,
The starting current control circuit includes an oscillation circuit that oscillates at a predetermined frequency,
A clock control circuit for generating a clock pulse based on the oscillation frequency of the oscillation circuit;
The input voltage is compared with the output voltage of the charge pump circuit, and when the input voltage becomes lower than the output voltage, the clock control circuit controls the drive of the charge pump circuit to change the current path, thereby limiting overcurrent. A step-up power supply circuit comprising a comparator. The overcurrent is limited by an error amplifier to which negative feedback is applied via a resistor and an overcurrent limit circuit, and the charge voltage is controlled by controlling the gate voltage of the transistor provided between the capacitor and GND which is the charge path of the charge pump circuit. In a boosting method for obtaining a fixed output by controlling the input current of the pump circuit,
A boosting method, wherein a comparator compares an input voltage with an output voltage, and a clock pulse control circuit controls a starting current of the charge pump circuit according to an output of the comparator. By controlling the gate voltage of the transistor provided between the capacitor, which is the charge path of the charge pump circuit, and the GND by limiting the overcurrent by the error amplifier and negative current feedback through the resistor and the overcurrent limiting circuit. In a boosting method for obtaining a fixed output by controlling the input current of the charge pump circuit,
Oscillates at a predetermined frequency by the oscillation circuit,
A clock control circuit generates a clock pulse based on the oscillation frequency of the oscillation circuit,
The comparator compares the input voltage with the output voltage of the charge pump circuit. When the input voltage becomes lower than the output voltage, the clock control circuit controls the drive of the charge pump circuit to change the current path. A voltage boosting method characterized by reducing a current limiting current.

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