JPH0526947Y2 - - Google Patents

Description

[Detailed description of the invention] [Purpose of the invention] (Field of industrial application) The invention relates to a switching regulator,
Particularly related to those employing the chiyotsupa method.

(Prior Art) Fig. 2 shows a conventional switching regulator employing the chopper method. This switching regulator includes a reference voltage generation circuit 16, a transistor 3 as a switching element, a resistor 4 for regulating the base current of the transistor 3, a differential amplifier circuit (error amplifier circuit) 17, a smoothing circuit 18, and a freewheeling diode ( It has a commutating diode) 9 and voltage dividing resistors 11 and 12 for output voltage detection.

The reference voltage generation circuit 16 short-circuits the gate and source of the FET (field effect transistor) 1.
It consists of FET1 and Zener diode 2 connected in series. The reference voltage value is almost determined by the specifications of Zener diode 2, but by operating FET 1 as a constant current circuit, the Zener current can be adjusted.
Iz is kept constant to improve the stability of the reference voltage.

The differential amplifier circuit 17 is constructed by connecting the emitters of transistors 5 and 7, and connecting an emitter resistor 6 between the emitters and a zero volt line (0V). The base of the transistor 5 is connected to the cathode side of the Zener diode 2 in the reference voltage generating circuit 16, and the collector is connected to the base of the transistor 3 via the resistor 4. The base of the transistor 7 is connected to the series connection point of the voltage dividing resistors 11 and 12, and the collector is connected to the smoothing circuit 18.
connected to the output side of the

The smoothing circuit 18 includes a chiyoke coil 8 connected to the collector of the transistor 3, and a capacitor 10 connected between the other end of the chiyoke coil 8 and the zero volt line.

In the above configuration, the constant voltage output of the reference voltage generation circuit 16 is applied to the base of the transistor 5,
The output voltage divided by the voltage dividing resistors 11 and 12 is applied to the base of the transistor 7. Therefore, the differential amplifier circuit 17 controls the switching operation of the transistor 3 based on the difference between the reference voltage and the smoothing circuit output voltage (self-excited chopper type). The switching output of the transistor 3 is connected to the choke coil 8 and the capacitor 1.
0, and a stable DC output can be obtained from the output end of the smoothing circuit 18.

By the way, such switching regulators are widely used as power supply circuits for various electronic devices, etc., but in recent years, due to the demand for smaller and cheaper electronic devices, etc., there has been a need to reduce the size and manufacturing costs of the switching regulator itself.

However, as long as the switching regulator is composed of discrete components, there is a limit to the miniaturization of the circuit board that forms the regulator and the reduction in manufacturing costs.As long as the circuit configuration shown in Figure 2 is adopted, the above requirements can be met. is becoming extremely difficult.

(Problems to be Solved by the Invention) As described above, in the conventional switching regulator, it is difficult to downsize the regulator itself and reduce manufacturing costs.

This invention was made in view of the above circumstances, and its purpose is to provide a switching regulator that can be made smaller and lower in manufacturing cost, as well as provide excellent stable DC output. There is a particular thing.

[Structure of the invention] (Means for solving the problems) The switching regulator of the invention includes a switching element that switches an input voltage, a smoothing circuit that smoothes the switching output of this switching element, and a switching element that switches an input voltage. a reference voltage generation circuit that is connected to the input side of the switching element and generates a reference voltage based on the input voltage; and a reference voltage generation circuit that generates a reference voltage based on the input voltage; A transistor connected to the switching element for controlling opening/closing operation and driven by a reference voltage from the reference voltage generation circuit, and a diode connected in a forward direction between the output side of the smoothing circuit and the emitter of the transistor. It has a differential amplifier circuit.

(Function) When a differential amplifier circuit is configured with two transistors 5 and 7 as in the conventional case (Fig. 2), the output voltage is divided and applied to the base of one transistor 7. Therefore, the voltage dividing resistors 11 and 12 are essential. Therefore, if a diode is used in place of this transistor 7 and the output of the smoothing circuit is taken into the differential amplifier circuit via this diode, the voltage dividing resistors 11 and 12 can be omitted.

By replacing one transistor of the differential amplifier circuit with a diode in this way, the voltage dividing resistor 1
1 and 12 can be omitted, the number of parts can be reduced, and the switching regulator itself can be made smaller and its manufacturing cost can be reduced.

(Example) Hereinafter, the present invention will be specifically explained with reference to Examples.

FIG. 1 is a circuit diagram of a switching regulator that is an embodiment of the present invention. In the figure, parts having the same functions as those shown in FIG. 2 are designated by the same reference numerals. This switching regulator differs from conventional ones in that the differential amplifier circuit 19 is
Transistor 5, emitter resistor 6, diode 1
3 and the voltage dividing resistor 1 in Fig. 2.
The point is that there is no equivalent to 1 and 12.
A silicon type diode is used as the diode 13, and its cathode side is connected to the emitter side of the transistor 5, and its anode side is connected to the output side of the chiyoke coil 8. A current flows in the forward direction of the diode 13 due to the output of the smoothing circuit 18, that is, the voltage applied to the capacitor 10, and this current changes the voltage across the emitter resistor 6, and this change causes the collector current of the transistor 5 to change. Change. Therefore, the differential amplifier circuit 19 composed of the transistor 5, the emitter resistor 6, and the diode 13 is as follows.
It operates similarly to the differential amplifier circuit 17 of FIG. 2, and can drive and control the chopper operation of the transistor 3. Note that the value of the output stable DC voltage is approximately equal to the Zener voltage of the Zener diode 2.

In this embodiment, the transistor 5 receives the output of the reference voltage generating circuit 16, the cathode side is connected to the emitter of the transistor 5, and the anode side is connected to the output side of the choke coil 8 of the smoothing circuit 18. 13 to constitute the differential amplifier circuit 19, the voltage dividing resistors 11 and 12 which were essential in the conventional regulator (FIG. 2) can be omitted.
The number of parts of the switching regulator itself can be reduced. Therefore, it is possible to reduce the size and manufacturing cost of the switching regulator.

As the Zener diode 2 in the reference voltage generation circuit 16, it is preferable to use a Zener diode with a small temperature coefficient and a Zener voltage of around 5V. for example
When HZ5C3 is applied, Zener current Iz≒1.8mA,
With a setting tolerance of 5V±2%, it is possible to suppress the reference voltage fluctuation with respect to temperature to within 1% (Ta = -40 to +85℃), and a stable DC output with excellent temperature characteristics can be obtained from the output terminal of the smoothing circuit 18. be able to. In this case, the stable DC output is 5V DC, which is in high demand as a power source for TTL (transistor-transistor logic) ICs.

It goes without saying that the present invention is not limited to the above-mentioned embodiments, and that various modifications can be made.

[Effects of the invention] According to the invention described in detail above, with the above-described configuration, size reduction and manufacturing cost can be reduced, and since the reference voltage generation circuit is provided on the input side of the switching element, It is possible to provide a switching regulator in which this reference voltage generation circuit does not affect the output voltage of the switching regulator and can obtain an excellent DC stable output.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a switching regulator according to an embodiment of the present invention, and FIG. 2 is a circuit diagram of a conventional switching regulator. 3...transistor (switching element), 5
...Transistor, 13...Diode, 16...
...Reference voltage generation circuit, 18...Smoothing circuit, 19...
...Differential amplifier circuit.

Claims (1)

[Scope of utility model registration request] a switching element that switches an input voltage; a smoothing circuit that smoothes the switching output of this switching element; a reference voltage generation circuit that is connected to the input side of the switching element and generates a reference voltage based on the input voltage; A transistor connected to the switching element and driven by the reference voltage from the reference voltage generation circuit, which controls the opening/closing operation of the switching element based on the difference between the reference voltage output from the voltage generation circuit and the smoothed output of the smoothing circuit. and a differential amplifier circuit comprising a diode connected in a forward direction between the output side of the smoothing circuit and the emitter of the transistor.