JP2002312041A - Switching regulator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a low-cost switching regulator assuring a low loss. SOLUTION: The switching regulator is furnished with an FET Q1 to open and close a DC power supply, a transistor Tr2 to control the gate voltage of the FET Q1, and a transistor Tr3 to control the gate voltage of the FET Q1 and the base voltage of the transistor Tr2, and from the input circuit side, control voltages are supplied to the gate of the FET Q1 and the base of the transistor Tr2, while a control voltage is supplied to the base of the transistor Tr3 from the output circuit side via a voltage dividing circuit consisting of resistances R5 and R6. In accordance with the voltage of the output circuit, the transistor Tr3 makes switching, and therewith the transistor Tr2 and FET Q1 make switching oppositely to the transistor Tr3, and the output circuit voltage is controlled constant.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a switching regulator, and more particularly, to a step-down switching regulator with improved efficiency.

[0002]

2. Description of the Related Art Switching regulators are roughly classified into an insulation type in which a switching element and a transformer are combined and a chopper type non-insulation type in which a transformer is not used. Although there are advantages in power efficiency and safety,
According to the electrical specifications of the switching regulator, the transformer is manufactured or ordered from a specialized manufacturer, resulting in high cost.

A chopper type switching regulator using an IC regulator can be constructed with high precision and small size, but includes a switching element, a reference voltage generator, an oscillator, a voltage comparator, a logic circuit and the like in one package. IC regulators are expensive and cost as much as transformers. Therefore, in order to reduce the cost of the regulator, the regulator is configured with a simpler circuit without using a transformer or an IC regulator.

FIG. 3 shows a conventional step-down regulator 1.
2 is a DC power supply, 3 is a load, C1 is a smoothing capacitor,
The configuration is such that the current of the transistor Q2 is controlled by the output voltage detected by the voltage dividing resistors R3 and R4, and the conduction of the transistor Q1 is controlled by the transistor Q2 to supply a constant voltage to the load.

In this step-down regulator, a base voltage is applied to the transistor Q2 from the output side circuit to supply a constant voltage to the load side. Therefore, even when the current of the transistor Q1 is small, power is consumed, and when the current is large, There is a problem that more power is consumed, loss is large, and efficiency is low.

Therefore, there arises a technical problem to be solved in order to provide a low-cost and low-loss regulator, and an object of the present invention is to solve the above problem.

[0007]

SUMMARY OF THE INVENTION The present invention proposes a first transistor or FET for opening and closing a DC power supply, and a base voltage of the first transistor or a gate of the first transistor. A second transistor that controls the voltage, a third transistor that controls the base voltage of the first transistor or the gate voltage of the FET and the base voltage of the second transistor, and the first transistor Provides a switching regulator with a circuit configuration that supplies a control voltage to the base or the gate of the FET and the base of the second transistor, and supplies a control voltage from the output circuit side to the base of the third transistor via the voltage dividing circuit. Is what you do.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below in detail with reference to the drawings. In FIG. 1, 11 is a step-down switching regulator, 12 is a DC power supply, 13 is a load,
The switching regulator 11 is connected to a DC power supply.
The gate of TQ1 is switched by transistors Tr2 and Tr3 to control the supply voltage to load 13 constant.

The input side circuit of the switching regulator 11 is grounded via the resistor R2, the transistor Tr3 and the Schottky barrier diode D1, and the gate of the FET Q1 is connected to the resistor R3.
And to the collector of the transistor Tr2 via a resistor R4. The base of the transistor Tr2 is connected between the resistor R2 and the transistor Tr3, and the emitters of the transistors Tr2 and Tr3 are resistors.
Connected to the input side circuit via R1. The output voltage of the FET Q1 is applied to the base of the transistor Tr3 via the voltage dividing resistors R5 and R6.

When the DC power supply 12 is turned on, through the resistor R3
A voltage is applied to the gate of the FET Q1, a current flows from the source to the drain of the FET Q1, and the transistor Tr3 is turned on and off according to the output voltage detected via the voltage dividing resistors R5 and R6.
The transistor Tr2 is turned on and off in the opposite direction to the transistor Tr3, so that the FET Q1 is switched at high speed, and operates so as to keep the output voltage constant regardless of the load change. Note that C2 is a smoothing capacitor, and C1 is a smoothing capacitor similar to a conventional step-down regulator.

When the output voltage is equal to or lower than the specified value, the transistor Tr3 is off and the transistor Tr2 and the FET Q1 are turned on by the voltage supplied from the input side circuit through the resistors R2 and R3.
Is turned on, and current is supplied from the FET Q1 to the load 13 and the smoothing capacitor C2.

When the output voltage reaches a specified value and the transistor Tr
When transistor 3 turns on, transistor Tr2 and FET Q1 turn off, and transistor Tr2 turns off, so that no current flows from the gate side circuit of FET Q1 through transistor Tr2, and power loss when FET Q1 is off is extremely small. .

Since the base current of the transistor Tr2 is supplied from the input side circuit, unlike the conventional step-down switching regulator which supplies the base current from the output side circuit as shown in FIG. 3, the FET Q1 and the transistor When the transistor Tr2 is on, the current of the output side circuit is not consumed by the transistor Tr2, so that the output loss and the output fluctuation related to the loss are reduced.

Also, as shown in FIG. 2, the same operation and effect as the above-described circuit can be obtained by using a transistor Tr1 instead of the FET Q1 as a switching element.

It should be noted that the present invention is not limited to the above embodiment, and various modifications are possible within the technical scope of the present invention, and it goes without saying that the present invention extends to those modifications. is there.

[0016]

As described above, the switching regulator of the present invention does not use expensive components such as a transformer and an IC regulator, so that the cost is low and the switching regulator is compared with a conventional step-down regulator which does not use a transformer. Loss is small, and the power conversion efficiency is improved.

[Brief description of the drawings]

FIG. 1 illustrates an embodiment of the present invention and is a circuit diagram of a switching regulator.

FIG. 2 is a circuit diagram of a switching regulator according to another embodiment.

FIG. 3 shows a conventional example, and is a circuit diagram of a step-down regulator.

[Explanation of symbols]

 11 Switching regulator 12 DC power supply 13 Load Q1 FET Tr2 transistor Tr3 transistor

Continued on the front page F term (reference) 5H430 BB01 BB11 EE06 FF02 FF13 GG02 HH02 5H730 AA14 AA15 AS05 BB03 BB52 DD04 DD27 EE07 EE59 FD03 FG01

Claims (1)

[Claims] 1. A first transistor or FET for opening and closing a DC power supply, and a base voltage or F of the first transistor.
A second transistor for controlling the gate voltage of the ET, and a third transistor for controlling the base voltage of the first transistor or the gate voltage of the FET and the base voltage of the second transistor; Circuit configuration that supplies a control voltage to the base of the transistor or the gate of the FET and the base of the second transistor, and supplies the control voltage from the output circuit side to the base of the third transistor via the voltage dividing circuit regulator.