JPS60125171A - Switching regulator circuit - Google Patents

Abstract

PURPOSE:To reduce the variation in the output voltage of a switching regulator circuit by employing a diode connection of a bipolar transistor as a unidirectional conduction element. CONSTITUTION:A sawtooth wave voltage generator is formed of resistors 300- 305, 309, transistors 310, 311, a capacitor 315, differential amplifiers 317, 318 the sawtooth wave is inputted to a comparator which has a resistor 306, a transistor 312 and a differential amplifier 319, compared with a control input Vin to output a rectangular wave having a duty proportional to the input Vin. In the stepdown circuit, a equivalent diode in which a resistor 308 and the base, collector of a pnp transistor 315 are connected between the collector of a transistor 313 and a GND is inserted.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is characterized in that current is passed intermittently from a power supply voltage higher than the output voltage by switching transistors, and further smoothed.
This invention relates to a switching regulator circuit that efficiently reduces voltage by circulating current.

A typical example of a conventional circuit that performs this function is shown in FIG. Further, signal waveforms at each location in FIG. 1 are shown in FIG. 2. In FIG. 1, numeral 10 is a sawtooth voltage generator (oscillator) which outputs the signal shown in FIG.

Next, a comparator 11 compares the sawtooth voltage with an external input voltage Vin (■ in FIG. 2) which uniquely determines the output voltage VOUT of the switching regulator circuit at the moment, and outputs a rectangular wave. When the output of the comparator is low, the pnp transistor 2 becomes 100N and supplies the current supplied from the power supply Vcc to the load 2 through the inductor 14.

Is capacitor 5 ON or OFF of transistor 2?
This is provided for the purpose of smoothing voltage or current pulsations due to The diode 13 is also called a flywheel diode and is the OF of the transistor 12. Sometimes inductor 1
The induced voltage generated in 4 causes the inductor, load, and G
ND is for passing the circulating current ε flowing in the forward path of the diode 16. The voltage waveform at the node of FIG. 1 is as shown in FIG. 2, and the enlarged waveform of the output voltage at the output terminal 17 is as shown in FIG. 2. As can be seen in Figure 2, a considerable spike voltage 22.20 occurs immediately after the diode 13 becomes conductive and immediately after it is cut off. This also appears in the output waveform (■) and becomes a serious problem in terms of output voltage stabilization. The magnitude of this spike voltage is 100 to 30 V compared to the magnitude of output voltage pulsation of 20 to 30 V.
There was a drawback that the voltage was as high as 200 V, which could not be ignored. The present invention provides a switching regulator circuit which improves the above disadvantages and significantly reduces the fluctuation rate of output voltage, and which is used as a power source for a drive circuit of a small motor and a speed control device that precisely controls the rotation speed of a motor. The purpose is to provide Next, the contents of the present invention will be explained in detail in order.

FIG. 3 shows an embodiment of the circuit according to the present invention. The names of each part in the figure are as follows. 300-309...
·resistance,! 110.31!1,314...PN
P transistor, 511, 312° 311...
NPN) transistor, 515, 316... capacitor, 317~'519... differential amplifier, 3
20... Inductor, 321... Control input voltage to the switching regulator circuit, 322... Output voltage terminal. The functions of the circuit are generally represented by the following blocks. As these blocks, resistors 500, 301, 302, 305, 50
9.303,304. ) The transistors 310, 311, the capacitors 3151, the differential amplifiers 317, 318 as a whole, and the blocks that make up the pressure generator, compare the magnitude of the sawtooth wave voltage ■ and the control human power Vin, and input it.
A block that outputs a rectangular wave with a density proportional to lj EE V 1n (this block consists of a circuit using a resistor 506, a transistor 612, and a differential amplifier 319 as a comparator), and a step-down voltage converter consisting of the remaining elements. and a block for the smoothing circuit. Figure 4 shows the voltage waveforms at the main parts of the circuit. Also, points in FIG. 3 that require special explanation will be explained. First in the sawtooth voltage generator (oscillator), resistor 300.301,5
02 and the transistor 310 together constitute a constant current source. This constant current charges the capacitor 315 and generates a voltage that rises at a constant slope over time. This voltage is output without being amplified by the buffer amplifier 317 and is output to the amplifier 318.
When the reference voltage Vref is reached, the transistor 3
11 and returns to the GND level. Next, in the step-down circuit, the difference from the conventional series (Figure 1) is the resistor 308 connected between the collector of transistor 313 and GND.
This is an equivalent diode that connects the base and collector of a PnP (PnP) transistor inserted in place of a diode. resistance 3
08 is for stabilizing the collector potential of the transistor 313, and its resistance value is as large as Ω compared to IP-10, and its contribution to the total current consumption can be ignored. The insertion of the transistor 314 is the main point of the present invention, and as shown by the voltage waveform 405 in FIG. 4, unlike the conventional array, no spike voltage is generated, as shown by 400 and 401 in the figure. Therefore, as an effect, the output voltage 406 (■) is stabilized.

Next, the characteristics exhibited by the switching regulator circuit according to the present invention will be explained. FIG. 5 1 shows the control input voltage Vin to the circuit concerned versus the output voltage VOUT. The controllable range is 1-6v. FIG. 6 shows the power conversion efficiency of the circuit, which shows a good value. The same characteristic is a value measured for an output power of 0 to 1W.

As explained above, the switching regulator circuit according to the present invention has a stable output voltage with small fluctuations, and is particularly suitable for driver circuits that precisely control the rotation speed of consumer devices using small motors. There are many possible benefits

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing a typical example of a switching regulator circuit. FIG. 2 is a diagram showing voltage waveforms of main parts in the circuit of FIG. 1. FIG. 3 is a circuit diagram showing an implementation 913 of the switching regulator circuit according to the present invention, and FIG. 4 is a diagram showing voltage waveforms similar to FIG. 2 in contrast to FIG. FIG. 5 is a diagram showing the input versus output voltage characteristics of the switching regulator (@Figure 4) according to the present invention. FIG. 6 is a diagram similarly showing the input versus power conversion efficiency of FIG. 4. 10... Sawtooth voltage generator (oscillator) 13...
Flyhole diode 14, which is a one-way conduction element... Inductor and above Applicant Suwa Seikosha Co., Ltd. Representative Patent Attorney Tsutomu Mogami Figure 4 - (V) No. 50 0 1 2 3 4 5 - (V) No. 6 figure

Claims (1)

[Claims] An oscillator that generates a sawtooth wave voltage, a comparator that compares the sawtooth voltage value with a reference voltage value input from the outside and outputs it, and one of the binary logic levels of the rectangular wave output of the comparator, A transistor that conducts current from a power supply, an inductor connected in series to the transistor, a capacitor for smoothing the output voltage, and a capacitor for smoothing the output voltage so that the load can maintain a constant current during the non-conducting period of the transistor. A switching regulator circuit having an element capable of conduction in only one direction in order to circulate current to the inductor, characterized in that a diode connection of a bipolar transistor is used as the one-way conduction element.