JP2002238251A - Power circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a highly efficient switching regulator circuit not dependent upon input voltage. SOLUTION: A booster circuit or an inversion circuit is built in a switching regulator control circuit to boost terminal voltage for driving an external transistor or output inverted voltage.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a switching regulator circuit capable of realizing a highly efficient switching regulator circuit with a simple circuit.

[0002]

2. Description of the Related Art As a conventional synchronous rectification step-down switching regulator circuit, a circuit as shown in a circuit diagram of FIG. 4 has been known. That is, the power supply 10 is connected to the external transistor 14, the other end of the external transistor is connected to the coil 16 and the external transistor 15, and the other end of the coil becomes the output terminal VOUT of the switching regulator circuit. The terminal has a capacity of 20
Is connected, and the switching regulator control circuit 17 controls the external transistor 14,
The ON time and the OFF time of the external transistor 15 are controlled. In the case of FIG. 4, the input voltage is supplied from the power supply 10, and the same voltage as the input voltage is also supplied from the VDD terminal 18 to the switching regulator control circuit. Therefore, the PDRV terminal 21 and the NDRV terminal 22 for driving the external transistor also operate with the voltage width from the input voltage to GND, and drive the external transistor with the input voltage width.

[0003]

However, in the conventional synchronous rectification step-down switching regulator circuit, when the input voltage is low, the terminal voltage of the terminal for driving the external transistor also becomes low similarly to the input voltage. . In such a case, since a sufficient voltage is not applied to the gate of the external transistor, the ON resistance of the external transistor increases and the efficiency is significantly reduced. Another problem is that the external transistor does not turn on. Also,
Depending on the application, when the input voltage range is wide and a high voltage is applied even for a moment, an external transistor that can withstand the high voltage must be selected. The external transistor selected in this manner is generally very difficult to turn on at a gate voltage of 2 to 5 V. Even if the external transistor is turned on, it has a very high ON resistance and significantly lowers the efficiency. was there.

[0004]

In order to solve such a problem, a switching regulator control circuit having a built-in boosting or inverting circuit is used to change the terminal voltage of a terminal for driving an external transistor to a voltage other than the input voltage. It is characterized in that output can be performed at a desired voltage.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, a terminal voltage for driving an external transistor is set to a desired voltage by incorporating a boosting or inverting circuit in a switching regulator control circuit.

[0006]

FIG. 1 is a power supply circuit diagram showing a first embodiment of the present invention. This is a circuit known as a synchronous rectification step-down switching regulator circuit.

Next, the operation will be described. The switching regulator control circuit 17 is supplied with an input voltage from a VDD terminal 18. Here, a boosting circuit 31 and an inverting circuit 32 exist inside the switching regulator control circuit 17. This is a booster circuit 31 that outputs a desired boosted voltage of the voltage supplied from the VDD terminal 18 and an inverting circuit 32 that outputs a desired inverted voltage. For example, the boosting circuit 31 and the inverting circuit 32 can be realized by being constituted by a charge pump circuit. The voltage boosted by the booster circuit 31 is supplied to the buffer 13 for driving the external transistor 15 as a power supply. The level shifter 33 is a circuit that shifts the level of a signal line supplied from the internal circuit 11 to the buffer 13 to a voltage at which the buffer 13 can be driven. Similarly, the level shifter 34 is a circuit for level-shifting a signal line provided from the internal circuit 11 to the buffer 13 to a voltage at which the buffer 12 can be driven. Here, the internal circuit 11 is driven by the voltage given from the VDD terminal 18.

In the above circuit, the NDRV terminal 22 for driving the external transistor 15 operates with a voltage width of GND from the voltage boosted by the booster circuit 31, and the PDRV terminal 21 for driving the external transistor 14
The operation is performed with the voltage width of the voltage inverted by the inversion circuit 32 from the input voltage.

According to the first embodiment of the present invention, only the input voltage width is applied to the external transistor 14 and the external transistor 15 in the related art. 32
Is provided, a voltage larger than the input voltage width is applied to the gate of each external transistor.

Here, when the input voltage is low (3 to 5
V). The external transistor 15 includes
Since the voltage boosted by the booster circuit inside the switching regulator control circuit is applied to the gate terminal instead of the low input voltage, the external transistor 15 operates with a sufficiently small ON resistance despite the low input voltage. . Similarly, since the voltage inverted by the switching regulator control circuit is applied to the gate terminal of the external transistor 14, the input voltage +
The inverted voltage is applied. Therefore, like the external transistor 15, the external transistor 14
Operates with a sufficiently small ON resistance despite the low input voltage.

FIG. 2 is a power supply circuit diagram showing a second embodiment of the present invention. The difference from the first embodiment is that a boosting or inverting circuit is not provided inside the switching regulator control circuit. However, the power of the internal circuit 11 and the buffer 12 is applied from the input voltage, but the power of the buffer 13 and the level shifter 32 is applied from the external capacitor 102. Further, as shown in FIG. 2, the external capacitor 102 is connected to a power supply via a diode 101.

Here, the operation of the second embodiment will be described. In the synchronous rectification step-down switching regulator circuit, the external transistor 14 and the external transistor 15 usually operate in synchronization with each other, and the output voltage VOU
Keep T at a constant voltage. Here, it is assumed that the external transistor 14 is turned on first and the external transistor 15 is turned off. The PDRV terminal 21 and the NDRV terminal each output a GND potential. In this state,
The external capacitor 102 is charged with a voltage difference corresponding to the input voltage via the diode 101.

Next, the external transistor 14 is turned off.
It is assumed that the external transistor 15 is in an ON state. Since the PDRV terminal 21 outputs the input potential, the external capacitor 10 previously charged to the input voltage is output.
The GND level of 2 is boosted by the PDRV terminal 21, and the voltage of the terminal 100 becomes twice the potential of the input voltage. Therefore, a voltage twice the input voltage is applied to the buffer 13 and the level shifter 33 as power. For this reason, a voltage twice as high as the input voltage is applied to the NDRV terminal.
The doubled voltage is applied to the external transistor 15, and the external transistor 15 can obtain a sufficiently small ON resistance even at a low input voltage.

The third embodiment has a circuit configuration similar to that of the second embodiment, except that the external transistor 14 is turned on.
To reduce the resistance, connect the external capacitor 112 to NDRV
Terminal 22 and one end is connected to G via a diode 111.
Connect to ND. Here, first, the external transistor 1
4 is turned off and the external transistor 15 is turned on. The PDRV terminal 21 and the NDRV terminal each output an input voltage. In this state, the external capacitor 112 is charged with a voltage difference corresponding to the input voltage.

Next, the external transistor 14 is turned on,
It is assumed that the external transistor 15 is in an OFF state. Since the NDRV terminal 22 outputs the potential of GND, the external capacitor 11 previously charged to the input voltage is output.
The high potential side of 2 is dropped to the GND level by the NDRV terminal 22, and the voltage of the terminal 110 is output by boosting the inverted potential of the input voltage. Therefore, the inverted potential of the input voltage is applied to the buffer 12 and the level shifter 34.
Is applied as GND. For this reason, the inverted voltage of the input voltage is applied to the NDRV terminal, and a voltage twice as high as the input voltage is applied to the external transistor 14 by simply connecting the capacitor and the diode. The transistor 14 has a sufficiently small ON resistance.

In the first embodiment of the present invention, it is clear that a sufficient effect can be obtained even with a low input voltage by incorporating either the booster circuit or the inverting circuit. Further, the second and third embodiments also show a method of simply boosting and inverting the gate voltage of the external transistor.
It is clear that a more effective result can be obtained with respect to those which can perform the inversion voltage. Further, in the present invention, the synchronous rectification step-down switching regulator circuit has been described, but a normal step-down switching regulator circuit, and a step-up switching regulator circuit,
It is obvious that the present invention is applied to the inverting type switching regulator circuit.

[0017]

According to the present invention, a high-efficiency switching regulator circuit can be realized with a simple circuit configuration by setting a voltage for driving an external transistor to a desired voltage regardless of an input voltage.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a power supply circuit according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram of a power supply circuit according to a second embodiment of the present invention.

FIG. 3 is an explanatory diagram of a power supply circuit according to a third embodiment of the present invention.

FIG. 4 is an explanatory diagram of a conventional power supply circuit.

[Explanation of symbols]

 Reference Signs List 10 power supply 11 internal circuit 12 to 13 buffer 14 to 15 external transistor 16 coil 17 switching regulator control circuit 18 VDD terminal 19 GND terminal 20 capacitance 21 PDRV terminal 22 NDRV terminal 31 booster circuit 32 inverting circuit 33 to 34 level shifter 101, 111 diode 102, 112 capacity

Claims (4)

[Claims] 1. A switching regulator circuit including a boosting or inverting circuit, wherein a terminal voltage of an output terminal for driving an external transistor can be output at a desired voltage other than an input voltage. 2. An output terminal for driving an external transistor by using a switching regulator control circuit that separates a buffer power supply line inside a switching regulator for driving an external transistor and a power supply line for other internal circuits. A switching regulator circuit capable of outputting a voltage at a desired voltage other than the input voltage. 3. An external transistor is driven by using a switching regulator control circuit, a diode, and a capacitor, which separate a buffer power supply line inside a switching regulator for driving an external transistor, a power supply line of other internal circuits, and the like. A switching regulator circuit capable of outputting a terminal voltage of an output terminal at a desired voltage other than an input voltage. 4. A step-down switching regulator circuit using a switching regulator control circuit, a diode, and a capacitor, which separate a buffer power supply line inside a switching regulator for driving an external transistor, and a power supply line of other internal circuits. A switching regulator circuit for outputting a voltage twice the input voltage to the gate of each external transistor.