WO2014109304A1

WO2014109304A1 - Switching power supply device

Info

Publication number: WO2014109304A1
Application number: PCT/JP2014/050046
Authority: WO
Inventors: 貴史吉實
Original assignee: 株式会社村田製作所
Priority date: 2013-01-09
Filing date: 2014-01-07
Publication date: 2014-07-17
Also published as: JPWO2014109304A1; CN104838575A; JP5794447B2; CN104838575B

Abstract

A pulse voltage is applied to one terminal of a resistance element (R1). One terminal of a resistance element (R2) is connected to the other terminal of the resistance element (R1). A capacitor (C1) is provided between the other terminal of the resistance element (R2) and ground. A diode (D1) and a capacitor (C2) are connected in parallel with the resistance element (R1), and a diode (D2) and a capacitor (C3) are connected in parallel with the resistance element (R2). The diode (D2) is arranged in the reverse direction with respect to the diode (D1). Transistors (Q1, Q2) have a control terminal connected to the other terminal of the resistance element (R2) to turn an input power supply (E1) on and off. A transformer (16) transforms the AC voltage generated by turning the transistors (Q1, Q2) on and off.

Description

Switching power supply

The present invention relates to a switching power supply device, and more particularly to a switching power supply device in which an input power supply applied to a switching element is intermittent based on a pulse voltage.

An example of this type of device is disclosed in Patent Document 1. According to this background art, a pulse voltage and a power supply voltage are applied to the base and collector of the emitter follower transistor, respectively. The power supply voltage is interrupted by the pulse voltage, whereby a similar pulse voltage appears at the emitter of the emitter follower transistor.

JP 60-134516 A (FIGS. 3 and 4)

However, if a transformer is provided after the emitter follower transistor, the harmonics of the pulse voltage cause resonance with the LC circuit formed by the inductor component of the transformer and the stray capacitance of the circuit, and overshoot and undershoot of the pulse voltage. As a result, the waveform characteristics of the output voltage may be deteriorated.

Therefore, a main object of the present invention is to provide a switching power supply device that can improve the waveform characteristics of the output voltage.

A switching power supply device according to the present invention (10: reference numeral corresponding to the embodiment; the same applies hereinafter) is connected to a first resistance element (R1) having one terminal to which a pulse voltage is applied and the other terminal of the first resistance element. A second resistive element (R2) having one terminal, a first capacitive element (C1) provided between the other terminal of the second resistive element and the ground, and a first rectifying element connected in parallel with the first resistive element (D1), a second rectifier element (D2) connected in parallel with the second resistor element in a direction opposite to the direction of the first rectifier element, one terminal of the first resistor element, and the other terminal of the second resistor element A switching element (Q1) having a control terminal connected to the second capacitor element (C2 to C3) having one terminal and the other terminal connected thereto, and a control terminal connected to the other terminal of the second resistor element (Q1). , Q2), and AC voltage generated by switching element switching That includes a transformer (16).

Preferably, the second capacitor element includes a second capacitor (C2) and a third capacitor (C3) connected in series with each other.

More preferably, the second capacitor is connected in parallel with the first resistance element, and the third capacitor is connected in parallel with the second resistance element.

The resistance value of the second resistance element may be different from the resistance value of the first resistance element.

Preferably, the switching element includes an NPN-type first transistor (Q1) having a collector to which an input power supply is applied, and a PNP-type second transistor having an emitter and a collector connected to the emitter and ground of the first transistor, respectively. Includes (Q2).

More preferably, an electrolytic capacitor (C4) having one terminal connected to the emitter of the first transistor and the other terminal connected to the primary coil of the transformer is further provided.

When the pulse voltage rises, the current flows into the first capacitor element through the second capacitor element. As a result, the terminal voltage of the first capacitor element, that is, the voltage applied to the control terminal of the switching element rises rapidly. When the potential of the second capacitive element rises, the current is supplied to one of the first resistance element and the second resistance element, and the first rectification element and the second rectification element connected in parallel with the other resistance element. Flows into the first capacitive element through one of the rectifying elements. At this time, an RC circuit is formed by the resistive element and the first capacitive element through which current is conducted. Overshoot caused by stray capacitance and the inductor component of the transformer is suppressed by the RC circuit thus formed.

When the pulse voltage falls, the current based on the charge accumulated in the first capacitor element flows backward through the second capacitor element. As a result, the terminal voltage of the first capacitor element, that is, the voltage applied to the control terminal of the switching element falls abruptly. When the potential of the second capacitor element is decreased, the current is supplied to the other resistor element of the first resistor element and the second resistor element, and the first rectifier element and the second resistor element connected in parallel to the one resistor element. The current flows back through one of the rectifying elements. At this time, an RC circuit is formed by the first capacitive element and the resistive element that conducts current. Undershoot caused by stray capacitance and the inductor component of the transformer is also suppressed by the RC circuit thus formed.

∙ Input power is interrupted by such switching elements. As a result, a voltage having a waveform close to a rectangular wave is output from the switching element and thus the transformer, and the waveform characteristics of the output voltage are improved.

The above object, other objects, features, and advantages of the present invention will become more apparent from the following detailed description of embodiments with reference to the drawings.

It is a circuit diagram which shows the structure of one Example of this invention. It is an illustration figure which shows the electric current path | route at the time of a pulse voltage starting to rise. It is an illustration figure which shows the electric current path | route after a pulse voltage rises. It is an illustration figure which shows the electric current path | route at the time of a pulse voltage beginning to fall. It is an illustration figure which shows the electric current path after a pulse voltage falls. (A) is a waveform diagram showing an example of a change in pulse voltage output from the voltage generation circuit, (B) is a waveform diagram showing an example of a change in pulse voltage applied to the base of a transistor, (C ) Is a waveform diagram showing an example of a change in pulse voltage appearing at the emitter of the transistor, and (D) is a waveform diagram showing an example of a change in AC voltage applied to the primary coil of the transformer. (A) is a waveform diagram showing an example of a change in pulse voltage applied to the base of the transistor, and (B) is a diagram in which capacitors C2 to C3, diodes D1 to D2 and resistors R1 to R2 are omitted from the embodiment of FIG. FIG. 4C is a waveform diagram showing an example of a change in the base voltage of the transistor in the case, and FIG. 8C shows an example of a change in the base voltage of the transistor when the capacitors C2 to C3 and the diodes D1 to D2 are omitted from the embodiment of FIG. It is a waveform diagram.

Referring to FIG. 1, the switching power supply device 10 of this embodiment includes a 24V input power supply (DC voltage source) E1. The negative terminal of the input power supply E1 is connected to the ground, and the positive terminal of the input power supply E1 is connected to the collector of the NPN transistor Q1. The emitter of the transistor Q1 is connected to the emitter of the PNP transistor Q2, and the collector of the transistor Q2 is connected to the ground.

The voltage generation circuit 12 includes an NPN transistor Q3 having an emitter connected to the ground. The collector of transistor Q3 is connected to one terminal of resistance element R3, the other terminal of resistance element R3 is connected to the positive terminal of DC power supply E2, and the negative terminal of DC power supply E2 is connected to the ground. Note that the output voltage of the DC power supply E2 is variable in the range of 10V to 18V. *

The clock generator 14 applies a clock pulse to the base of the transistor Q3. The transistor Q3 is turned on / off in response to the clock pulse, whereby a pulse voltage (rectangular wave voltage) appears at one terminal of the resistance element R3. The pulse voltage indicates an L level when the transistor Q3 is in an on state, and indicates an H level when the transistor Q3 is in an off state.

One terminal of the resistance element R3 is connected to the bases (= control terminals) of the transistors Q1 and Q2 via the resistance elements R1 and R2 connected in series with each other. A capacitor C2 and a diode D1 are connected in parallel to the resistor element R1, and a capacitor C3 and a diode D2 are connected in parallel to the resistor element R2. The bases of the transistors Q1 and Q2 are also connected to the ground via the capacitor C1.

Here, the cathode of the diode D1 is connected to one terminal of the resistance element R1 (= one terminal of the resistance element R3), while the cathode of the diode D2 is connected to the other terminal of the resistance element R2 (= the bases of the transistors Q1 and Q2). Connected. That is, the diodes D1 and D2 are arranged in opposite directions.

The emitters of the transistors Q1 and Q2 are connected to the plus terminal of an electric field capacitor C4 that functions as a coupling capacitor. The negative terminal of the electric field capacitor C4 is connected to one terminal of the primary coil L1 that forms the transformer 16 and the other terminal is connected to the ground. Regarding the secondary coil L2 forming the transformer 16, one terminal is connected to the output terminal Vout, and the other terminal is connected to the ground.

The operational amplifier 18 controls the voltage of the DC power supply E2 based on the secondary voltage of the transformer 16. The secondary voltage of the transformer 16, that is, the AC voltage output from the output terminal Vout is adjusted to a desired value by such feedback control.

At the rise of the pulse voltage appearing at one end of the resistance element R3, the current based on the pulse voltage flows into the capacitor C1 through the capacitors C2 and C3 that are more likely to flow (see FIG. 2). As a result, the terminal voltage of the capacitor C1, that is, the base voltages of the transistors Q1 and Q2 rapidly increase.

When the potentials of the capacitors C2 and C3 rise, a current based on the pulse voltage flows into the capacitor C1 through the resistance element R1 and the diode D2 (see FIG. 3). At this time, an RC circuit is formed by the resistor element R1 and the capacitor C1. The amount of current flowing through the resistance element R1 depends on the resistance value of the resistance element R1, and the rising speed of the terminal voltage of the capacitor C1 due to the current flow depends on the capacitance of the capacitor C1.

Therefore, as the resistance value of the resistance element R1 increases or as the capacitance of the capacitor C1 increases, the increase in the terminal voltage of the capacitor C1 is delayed. As a result, the waveform of the rising terminal voltage is reduced, and overshoot is suppressed.

When the pulse voltage that appears at one end of the resistance element R3 falls, the current based on the charges accumulated in the capacitors C1 to C3 flows backward to the voltage generation circuit 12 (see FIG. 4). As a result, the terminal voltage of the capacitor C1, that is, the base voltages of the transistors Q1 and Q2 are rapidly reduced.

When the potentials of the capacitors C2 and C3 decrease based on the backflowed current, the current based on the charge accumulated in the capacitor C1 flows back to the voltage generation circuit 12 through the resistance element R2 and the diode D1 (see FIG. 5). At this time, an RC circuit is formed by the resistor element R2 and the capacitor C1. As described above, the amount of current flowing through the resistor element R2 due to the discharge of the capacitor C1 depends on the resistance value of the resistor element R2, and the rate of drop of the terminal voltage of the capacitor C1 due to the discharge depends on the capacitance of the capacitor C1.

Therefore, as the resistance value of the resistance element R2 increases or the capacitance of the capacitor C1 increases, the terminal voltage drop of the capacitor C1 is delayed. As a result, the waveform of the falling terminal voltage is reduced, and undershoot is suppressed.

As a result, when the pulse voltage output from the voltage generation circuit 12 changes as shown in FIG. 6 (A), the base voltages of the transistors Q1 and Q2 are as shown in FIG. 6 (B) or FIG. 7 (A). Change. According to FIG. 6 (B) or FIG. 7 (A), the waveform of the base voltage becomes sharp in the vicinity of the H level after suddenly rising, and in the vicinity of the L level (= 0 V) after sharply falling. Namaru.

For reference, FIG. 7B shows an example of changes in the base voltages of the transistors Q1 to Q2 when the capacitors C2 to C3, the diodes D1 to D2 and the resistors R1 to R2 are omitted from the circuit shown in FIG. FIG. 7C shows an example of changes in the base voltages of the transistors Q1 to Q2 when the capacitors C2 to C3 and the diodes D1 to D2 are omitted from the circuit shown in FIG.

According to FIG. 7B, since there is no RC circuit, overshoot and undershoot appear in the waveform of the base voltage. Further, according to FIG. 7C, the waveform of the base voltage is rounded depending on the time constant of the RC circuit.

When the base voltage changes as shown in FIG. 6B or FIG. 7A, the input power source E1 is interrupted, and a similar voltage waveform appears at the emitters of the transistors Q1 and Q2 (see FIG. 6C). ). The emitter voltage is 18V during the period when the base voltage is at the H level, and is 0V when the base voltage is at the L level.

The direct current component of the emitter voltage thus generated is eliminated by the electrolytic capacitor C4, whereby an alternating voltage having a maximum amplitude of 9 V is applied to the primary coil L1 of the transformer 16 (see FIG. 6D). An AC voltage corresponding to the transformation ratio of the transformer 16 appears at the secondary coil L2 of the transformer 16 and thus at the output terminal Vout.

With the configuration as described above, the switching power supply device 10 of this embodiment has the following effects.

That is, an AC voltage waveform corresponding to high-speed switching between L level and H level can be formed at low cost without using a high-speed high-speed operational amplifier. In addition, since an operational amplifier that is not susceptible to noise is used, noise resistance can be improved. Further, it is not necessary to route the pattern of the printed circuit board, and it is possible to avoid the decrease in the substrate design efficiency due to the pattern routing, which has been a problem in the high-speed operational amplifier. Further, since the active passive element is different between the rising time and the falling time of the pulse voltage, the voltage waveform at the rising portion and the voltage waveform at the falling portion can be adjusted independently.

In this embodiment, the cathode of the diode D1 is connected to one terminal of the resistance element R1 (= one terminal of the resistance element R3), and the cathode of the diode D2 is the other terminal of the resistance element R2 (= the bases of the transistors Q1 and Q2). ). However, instead of this, the anode of the diode D1 may be connected to one terminal of the resistor element R1, and the anode of the diode D2 may be connected to the other terminal of the resistor element R2.

In this embodiment, the resistance value of the resistance element R1 and the resistance value of the resistance element R2 are the same. However, the resistance values may be different between the resistance elements R1 and R2. This makes it possible to make a difference between the degree of rounding at the rising part of the base voltage and the degree of rounding at the falling part of the base voltage.

DESCRIPTION OF SYMBOLS 10 ... Switching power supply device 12 ... Voltage generation circuit 16 ... Transformer 18 ... Operational amplifier

Claims

A first resistance element having one terminal to which a pulse voltage is applied;
A second resistance element having one terminal connected to the other terminal of the first resistance element;
A first capacitive element provided between the other terminal of the second resistive element and the ground;
A first rectifying element connected in parallel with the first resistance element;
A second rectifying element connected in parallel with the second resistance element in a direction opposite to the direction of the first rectifying element;
A second capacitor element having one terminal and the other terminal connected to one terminal of the first resistor element and the other terminal of the second resistor element, respectively;
A switching power supply device comprising: a switching element that has a control terminal connected to the other terminal of the second resistance element and that interrupts an input power supply; and a transformer that transforms an AC voltage generated by the interruption of the switching element.
The switching power supply device according to claim 1, wherein the second capacitor element includes a second capacitor and a third capacitor connected in series with each other.
The second capacitor is connected in parallel with the first resistive element;
The switching power supply device according to claim 2, wherein the third capacitor is connected in parallel with the second resistance element.
4. The switching power supply device according to claim 1, wherein a resistance value of the second resistance element is different from a resistance value of the first resistance element.
The switching element includes an NPN-type first transistor having a collector to which the input power is applied, and a PNP-type second transistor having an emitter and a collector connected to the emitter and ground of the first transistor, respectively. The switching power supply device according to claim 1.
The switching power supply device according to claim 5, further comprising an electrolytic capacitor having one terminal connected to the emitter of the first transistor and the other terminal connected to a primary coil of the transformer.