JPH05292735A - Step-down type switching regulator - Google Patents

Abstract

PURPOSE:To reduce current consumption of an IC for controlling a step-down type switching regulator. CONSTITUTION:An oscillator 10 is supplied from an output voltage terminal 2 of a step-down type switching regulator. A transistor 15 and a switching transistor 3 having the same conductivity type are connected in parallel. A gate of the transistor 15 is driven by an output of a comparator 16 which is connected at one input with the output terminal of a reference voltage circuit 9 and at the other input with one voltage terminal of a bleeder resistor 12 connected to the terminal 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a step-down switching regulator.

[0002]

2. Description of the Related Art The circuit configuration of a conventional step-down switching regulator is shown in FIG. The switching transistor 3 and the inductor 4 are connected between the positive power supply input terminal 1 and the output voltage terminal 2, and the diode 5 is connected between the connection point and the ground point. This is called a chopper type step-down switching regulator. In order to control the output terminal voltage, bleeder resistors 6 and 7 are connected between the output voltage terminal 2 and the ground point, and the connection point is connected to the input terminal of the error amplifier 8. The output terminal of the reference voltage circuit 9 is connected to the other input terminal of the error amplifier 8. Further, the output terminal of the error amplifier 8 is connected to one input terminal of the NAND circuit 11 having the output terminal of the oscillation circuit 10 as the other input terminal.

The output terminal of the NAND circuit 11 is connected to the gate of the switching transistor 3. Normally, the switching transistor 3, the bleeder resistor 6,
7, error amplifier 8, reference voltage circuit 9, oscillator circuit 10, N
The AND circuit 11 is integrated into one chip and provided as a switching transistor control IC.

Then, the error amplifier 8, the reference voltage circuit 9 and the N constituting the step-down switching regulator are provided.
AND circuit 11, and further oscillation circuit 1 with large current consumption
The positive power supply voltage of 0 is also driven by the voltage input from the positive power supply input terminal 1.

[0005]

As described above, since the oscillator circuit consumes a large amount of current, it occupies a large part of the current consumption of the conventional step-down switching regulator.
Therefore, it has been required to reduce the current consumption of the oscillation circuit. In general, the current consumption of an oscillation circuit composed of CMOS is represented by the product of the oscillation frequency f, the gate capacitance C, and the positive power supply input voltage V.

That is, if the oscillation frequency is deviated, it is proportional to the positive power supply input voltage V. The present invention pays attention to the above points, and the input power source is the positive power source input terminal 1 as described above.
The voltage of the conventional oscillation circuit 10 supplied from the above is taken from the output voltage terminal, which is a lower voltage, to reduce the current consumption. Another object of the present invention is to provide a step-down switching regulator in which the oscillator circuit instantly starts operating even when the voltage of the output voltage terminal is zero when the positive power source is turned on.

[0007]

The means adopted by the present invention to achieve the above objects are as follows. Connect a transistor of the same polarity in parallel with the switching transistor of the step-down switching regulator,
It is characterized in that a branch terminal of a bleeder resistor provided in the step-down switching regulator and an output terminal of a reference power supply circuit are connected to the gate of the output terminal of a comparator having two input terminals.

[0008]

With the above structure, immediately after the positive power supply is turned on,
Even if the output terminal voltage is zero, the comparator detects the state and drives the transistor connected in parallel to bring the positive power supply voltage and the output terminal into conduction. Therefore, the output voltage terminal immediately rises and the oscillation circuit operates at a voltage lower than the positive power supply voltage. Therefore, the step-down switching regulator operates normally.

[0009]

1 is a circuit diagram of a step-down switching regulator of the present invention. The positive power supply input terminal 1 and the source of the switching transistor 3 are connected, and the drain thereof is connected to the inductor 4 and the cathode of the diode 5. The other end of the inductor 4 serves as the output voltage terminal 2, to which the bleeder resistors 6, 7, 12 and the capacitor 13 are connected. The connection point of the bleeder resistors 6 and 7 is connected to the negative input terminal of the error amplifier 8, and the voltage at the connection point is compared with the voltage of the reference voltage circuit 9 connected to the positive input terminal of the error amplifier 8. When the voltage at the connection point between the bleeder resistors 6 and 7 is higher than the voltage of the reference voltage circuit 9, the output of the error amplifier 8 becomes Low level, and the output of the NAND circuit 11 becomes High level. By this, N
Oscillation circuit 10 input to the other terminal of AND circuit 11
Cut off the oscillation waveform of the
FF. As a result, the voltage at the output voltage terminal 2 is separated from the positive input power supply voltage and drops.

Here, the positive power source of the oscillator circuit 10 is an arrow 14
It is supplied from the output voltage terminal 2 as shown by. Further, a transistor 15 having the same polarity is connected in parallel with the switching transistor 3 so that its drain and source are connected together, and its gate is connected to the output terminal of the comparator 16. The negative input terminal of the comparator 16 is the reference voltage circuit 9
The positive input terminal is connected to the connection point of the bleeder resistors 6 and 12.

In the step-down regulator, the voltage at the output voltage terminal 2 is naturally lower than the voltage at the positive power supply input terminal 1. Therefore, if the positive power supply of the oscillation circuit 10 is supplied from the output voltage terminal 2, the consumption current of the oscillation circuit 10 can be reduced because the consumption current is proportional to the applied voltage. But,
Immediately after applying the voltage to the positive power supply input terminal 1, the switching transistor 3 is in the OFF state, and therefore the voltage of the output voltage terminal 2 is zero. As a result, the oscillation circuit 10 to which the positive power supply is supplied from the output voltage terminal 2 does not start the oscillation because the voltage is not applied. That is, the control IC
Will not function.

Therefore, it is the transistor 15 and the comparator 16 that are provided so that the function of the control IC works immediately after the voltage is applied to the positive power supply input terminal 1. Since the positive power source of the comparator 16 is supplied from the positive power source input terminal 1, the comparator operation starts when a voltage is applied to the positive power source input terminal 1. At this time, the reference voltage circuit 9
Although not shown, the positive power source is also supplied from the positive power source input terminal 1, so that the operation is started. When the positive power source is input, the voltage at the output voltage terminal 2 is zero as described above, so the voltage at the connection point between the bleeder resistors 6 and 12 is also zero.

Therefore, the output of the comparator 16, that is, the gate voltage of the additional transistor 15 becomes the ground potential. As a result, the transistor 15 is turned on, a current path is formed between the positive power supply input terminal 1 and the output voltage terminal 2, and the voltage of the output voltage terminal 2 rises. If a voltage is generated at the output voltage terminal 2, the oscillation circuit 1 that uses this as a positive power supply
0 starts oscillation. Further, when the voltage of the output voltage terminal 2 rises and the voltage at the connection point of the bleeder resistors 6 and 12 becomes higher than the output voltage of the reference voltage circuit 9, the comparator 16 inverts and its output becomes the voltage of the positive power supply input terminal 1. They become equal and turn off the transistor 15. At this point in time, as described above, the oscillation circuit 10 has already started oscillating, so that the function of the control IC is activated to start the step-down operation.

The positive power source of the NAND circuit 11 is supplied from the positive power source input terminal 1, and the positive power source of the error amplifier 8 is supplied from either the positive power source input terminal 1 or the output voltage terminal 2. It satisfies the invention.

[0015]

As described above, according to the present invention, by providing means for generating a voltage at the output voltage terminal when the positive power supply voltage is applied, an oscillation circuit to which a positive power supply is supplied from the output voltage terminal is provided. Can be activated. As a result, since the oscillation circuit can be driven at a low voltage, there is an effect that a step-down switching regulator control IC with low current consumption can be realized.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a step-down switching regulator of the present invention.

FIG. 2 is a circuit diagram of a conventional step-down switching regulator.

[Explanation of symbols]

 3 Switching transistor 10 Oscillation circuit 15 Transistor 16 Comparator

Claims (1)

[Claims] 1. A series circuit in which a switching transistor and an inductor are connected in series between a positive power supply input terminal and an output terminal, a cathode is connected to a connection point of the switching transistor and the inductor, and an anode is grounded. A diode, a bleeder resistor connected between the output terminal and ground, an error amplifier having two input terminals of a branch terminal of the bleeder resistor and an output terminal of the reference voltage circuit, and an output terminal of the error amplifier. Connect the output terminal of the oscillator circuit to 2
In a step-down switching regulator consisting of a NAND circuit having one input terminal and an output terminal connected to the gate of the switching transistor, a transistor of the same polarity is connected in parallel to the switching transistor, and the gate is connected to the gate of the switching transistor. Is the branch terminal of the bleeder resistor and the output terminal of the reference power supply circuit.
A step-down switching regulator characterized in that the output terminals of a comparator that is one input terminal are connected.