JPH05161346A - Dc-dc converter - Google Patents

Abstract

PURPOSE:To equalize the capacities of the both output terminals even in the case that load is added to the first and the second output terminals. CONSTITUTION:Capacitors C2 and C3 are selectively charged to input power source VCC and earth potential, and then the connection of the capacitors C2 and C3 is changed by switches S1-S8 in response to an external control signal, and positive and negative output voltage occurs in output terminals VDD and VSS. Since the capacitors C2 and C3 are charged independently, the capacities of changing the output voltages become equal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charge pump type DC which outputs a double voltage and (-2) times the input voltage.
-DC converter, and more particularly, to a method of generating an output voltage.

[0002]

2. Description of the Related Art A conventional charge pump type C-DC converter is shown in FIG. 4 and its operation is shown in FIG.
The conventional DC-DC converter is composed of capacitors C5 to C8 and switches S9 to S16, and the switches S9 to S16 are switched from (a) of FIG.
It is set to repeat (b) → (c).
In the state of (a), the capacitor C6 is charged to the input voltage Vcc, and in the state of (b), the capacitor C6 is charged to VDD.
A capacitor C7 is connected between the terminal and VCC and between the VDD terminal and GND. At this time, a potential twice as high as VCC is generated at the VDD terminal, the potential at the VDD terminal is held by the capacitor C5, and the capacitor C7 is charged with the potential twice as high as VCC. In the state of (c), the capacitor C7 becomes GND-
It is connected to the VSS terminal, a potential of (−2) × VCC is generated at the VSS terminal, and the potential of the VSS terminal is held by the capacitor C8.

As described above, the state of the DC-DC converter repeats (a) → (b) → (c), and the VDD terminal and V
Voltages of 2 × Vcc and (−2) × Vcc are generated at the SS terminals, respectively.

[0004]

As described above,
The conventional charge pump type DC-DC converter converts the input power supply VCC to generate a potential at the VDD terminal.
The potential of the terminal was further converted to generate the potential on the VSS terminal. However, when a load is applied to the VDD terminal and the VSS terminal, the voltage conversion efficiency drops, and the VDD terminal voltage becomes low. And, since the lowered VDD pin voltage is output to the VSS pin with low conversion efficiency, the VSS pin voltage is lowered by two conversions as compared with the VDD pin voltage is lowered by one conversion. there were.

[0005]

The gist of the first invention of the present application is as follows.
The first output voltage that is an integer multiple of the input voltage is output to the first output terminal.
D including a charge pump circuit for respectively generating a second output voltage, which is an inverted value of the first output voltage, at a second output terminal
In a C-DC converter, an input voltage and a ground voltage are supplied to a first capacitor and a second capacitor, respectively,
The second capacitor converts the voltage of the second capacitor to generate the first output voltage at the first output terminal, the first capacitor is disconnected from the first output terminal to supply the ground voltage, and the first capacitor converts the voltage of the second capacitor. And a switch network for generating a second output voltage at the second output terminal.

The gist of the second invention of the present application is that a first output voltage obtained by multiplying an input voltage by an integer is generated at a first output terminal, and a second output voltage that is an inverted value of the first output voltage is generated at a second output terminal. A DC-DC converter including a charge pump circuit for supplying an input voltage and a ground voltage to both electrodes of a first capacitor respectively, and supplying an input voltage to a ground voltage side electrode of the first capacitor for voltage conversion and a first output First on the terminal
Generates an output voltage, supplies the input voltage and ground voltage to both electrodes of the second capacitor, supplies the ground voltage to the input voltage side electrode of the second capacitor, converts the voltage, and outputs the second output voltage to the second output terminal. Is to have a switch network for generating.

[0007]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a circuit diagram showing a first embodiment of the present invention, and FIG. 2 shows its operation.

The first embodiment comprises capacitors C1 to C4 and switches S1 to S8.
Are using. External control signal is switch S
1 to S8 are supplied so as to repeat the states (a) → (b) → (a) → (c). In the state (a), the capacitors C2 and C3 are charged to the potential of Vcc. In the state of (b), the capacitor C2 and the capacitor C3 are connected in series between the VDD terminal and GND, and
A potential of 2 × VCC is generated at the terminal, and the potential of the VDD terminal is held by the capacitor C1. Next, when returning to the state of (a), the capacitors C2 and C3 are charged again, and in the state of (c), the capacitors C2 and C3 are connected in series between the GND and VSS terminals, and the VSS terminal is -2 ×. The potential of Vcc is generated and the potential of the VSS terminal is held by the capacitor C4.

As described above, the present embodiment changes the state from (a) to
By repeating (b) → (a) → (c), potentials having the same ability are generated at the VDD terminal and the VSS terminal. Therefore, even if the voltage conversion efficiency is caused by the load, the VDD terminal and the VSS terminal are reduced to the same extent.

FIG. 3 shows the operation of the second embodiment. The circuit configuration is similar to that of the first embodiment. In the second embodiment, the external control signal is set so that the states repeat (a) → (b) → (c) → (d). (A)
In this state, only the capacitor C2 is charged. In the state (b), by connecting the capacitor C2 between the VDD terminal and VCC, the states (c) and (d) in which a potential of 2 × VCC is generated at the VDD terminal are the states (a) of the first embodiment. ，
It corresponds to (c).

In the second embodiment, the number of times the capacitor C3 is charged is half that in the first embodiment, and the current consumption of the entire circuit can be reduced. In the above embodiment, the capacitor C2 functions as the first capacitor and the capacitor C3 functions as the second capacitor. Switch network is S1-S
It is composed of 8. The capacitors C1 and C4 are
Functions as a fourth capacitor.

[0012]

As described above, according to the present invention, the method of generating the VDD terminal voltage and the VSS terminal voltage is directly converted from the capacitor charged with the power source voltage VCC, so that the VDD terminal and the VSS terminal are loaded. However, even if the voltage conversion efficiency is lowered due to the above, the voltage drop at the VDD terminal and the VSS terminal is equally reduced, and only one conversion is required.

[Brief description of drawings]

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

FIG. 2 is a state diagram showing the operation of the first embodiment.

FIG. 3 is a state diagram showing the operation of the second embodiment.

FIG. 4 is a circuit diagram showing a conventional charge pump type DC-DC converter.

FIG. 5 shows an operation of a conventional example.

[Explanation of symbols]

 S1 to S16 switches C1 to C8 capacitors VCC power supply terminals VDD and VSS output terminals

Claims (3)

[Claims] 1. A charge pump circuit for generating a first output voltage, which is an integer multiple of an input voltage, at a first output terminal and a second output voltage, which is an inverted value of the first output voltage, at a second output terminal, respectively. In a DC-DC converter, an input voltage and a ground voltage are supplied to a first capacitor and a second capacitor, respectively, and the first capacitor is voltage-converted by the second capacitor to generate a first output voltage at a first output terminal. DC-characterized by having a switch network for disconnecting one capacitor from the first output terminal to supply a ground voltage and converting the voltage of the second capacitor by the first capacitor to generate the second output voltage at the second output terminal DC converter. 2. A charge pump circuit for generating a first output voltage, which is an integer multiple of the input voltage, at a first output terminal and a second output voltage, which is an inverted value of the first output voltage, at a second output terminal, respectively. In a DC-DC converter, an input voltage and a ground voltage are respectively supplied to both electrodes of a first capacitor, an input voltage is supplied to a ground voltage side electrode of the first capacitor, and voltage conversion is performed to a first output voltage at a first output terminal. Occurs,
A switch network that supplies the input voltage and the ground voltage to both electrodes of the second capacitor, respectively, and supplies the ground voltage to the input voltage side electrode of the second capacitor to convert the voltage to generate the second output voltage at the second output terminal. A DC-DC converter having. 3. The third capacitor for maintaining the first output voltage is connected to the first output terminal, and the fourth capacitor for maintaining the second output voltage is connected to the second output terminal. Item 2. The DC-DC converter according to Item 1 or 2.