JPH04178165A - Dc voltage boosting power supply - Google Patents

Abstract

PURPOSE:To prevent generation of noise of audio system by providing a voltage setting device which sets an AC output of an oscillator to the predetermined level by rectifying an AC voltage generated on an intermediate tap provided to a secondary coil of an oscillation transformer in order to make negative feedback to the oscillator. CONSTITUTION:An output voltage of an oscillator 101 at the intermediate tap 230 of a secondary coil 232 of a transformer 23 is rectified by a diode 28 and smoothed by a smoothing capacitor 29. A DC output is then sent to an output terminal C. When an output voltage of the oscillator 101 at the intermediate tap 230 becomes higher than a zener voltage of a constant voltage diode 30, it becomes conductive and a base current flows into the base of a transistor 31. A collector voltage of the transistor 31 is lowered, a negative feedback is applied to the oscillator 101, a base voltage of transistor 26 is also lowered and an oscillation output level of transistor 26 is returned to the predetermined setting level. Thereby, even when a difference between an input voltage and an output voltage is eliminated, oscillation is continued and stable and boosted DC voltage can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a DC step-up power supply device used in audio equipment and the like.

BACKGROUND ART FIG. 2 shows a block diagram of a general DC step-up power supply device. In FIG. 2, 1 is an input power source, which is usually a dry battery. Reference numeral 2 denotes an oscillation section, which converts DC input into AC and outputs it.

3 is a rectifier, which outputs DC in response to the AC input from the oscillation unit 2. Reference numeral 4 denotes a voltage setting section which obtains a stable DC output by rectifying the alternating current in the rectifying section 3 and then applying negative feedback to the level of the oscillating section 2 depending on the voltage level.

In the above-mentioned general DC step-up power supply device, the DC voltage DC of the input power source is applied to the oscillation section 2, and this DC voltage is exchanged into the AC voltage AC by the oscillation section 2 and output to the rectification section 3. The rectifier 3 rectifies this alternating current voltage AC to convert it into a direct current voltage DC.
This direct current voltage DC is applied to the voltage setting section 4.

The voltage setting section 4 applies negative feedback to the oscillation section 2 according to the level of the direct current voltage DC rectified by the rectification section 3, thereby stabilizing the output voltage of the rectification section 3.

FIG. 3 shows the simplest conventional circuit diagram of the DC step-up power supply device. In FIG. 3, 5 is a dry battery, 6 is a capacitor for stabilizing the input power supply, and 7 is a transformer that constitutes an oscillation section. One end of the secondary winding 72 is connected to the positive electrode of the dry battery 5, and the other end is a transistor. It is connected to 11 collectors.

One end of the primary winding 71 of the transformer 7 is connected to the base of the transistor 11 via a resistor 8 and a capacitor 9. 10 is a resistor connected between the base of the transistor 11 and the positive electrode of the dry battery 5. The transformer 7, resistor 8, capacitor 9, resistor 10, and transistor 11 constitute an oscillation section K.

Further, 12 is a rectifying diode, the anode of which is connected to the collector of the transistor 11, and the cathode of which is connected to the output terminal A of the DC step-up power supply device. 1
3 is a smoothing capacitor whose one end is connected to the output terminal A of the present DC step-up power supply device, and the other end is grounded. The diode 12 and the smoothing capacitor 13 constitute a rectifier.

14 is a transistor whose collector is connected to the base of the transistor 11 and whose emitter is grounded; 15 is a voltage setting transistor whose anode is connected to the base of the transistor 16 and whose cathode is connected to the cathode of the diode 12; It is a constant voltage diode. 15 is
This resistor has one end connected to the base of the transistor 16 and the other end grounded. The transistor 14, the constant voltage diode 15, and the resistor 16 constitute a constant voltage setting section M.

Next, the operation of the conventional example shown in FIG. 3 will be explained. The DC voltage of the dry battery 5 is applied to the secondary winding 72 of the transistor in the oscillation section.
is applied to the collector of transistor 11 via
The voltage of the dry battery 5 is applied to the base of the transistor 11 through the resistor 10, and the transistor 11 oscillates with a time constant due to the resistor 8 and capacitor 9.

This oscillation generates an alternating current voltage at the collector of the transistor 11. This alternating current voltage is rectified by a diode 12, smoothed by a smoothing capacitor 13, and then sent to an output terminal A.
A DC voltage boosted from the voltage of the dry battery 5 is obtained.

Further, when the DC voltage appearing on the cathode side of the diode 12 exceeds the zener voltage of the voltage regulator diode 15, the voltage regulator diode 15 becomes conductive, negative feedback is applied to the base of the transistor 14, and the transistor 14 is turned on. The oscillation output voltage of transistor 11 is suppressed, and the DC voltage appearing at output terminal A is controlled to a predetermined voltage.

In this way, by controlling the level of the oscillation section mainly composed of the transistor 11, a stable boosted DC current can be obtained.

In this way, in the above conventional DC step-up power supply device, when the output voltage is sufficiently larger than the input voltage, the AC waveform at the output end B of the oscillation section is stabilized, as shown in FIG. The DC current at the output terminal A point after rectification by the diode 12 and the smoothing capacitor 13 has less ripple.

Problems to be Solved by the Invention However, in the above conventional DC step-up power supply device, when the voltage value of the input type voltage becomes close to the voltage value of the output voltage and becomes cloudy, excessive negative feedback is applied, and the fifth As shown in Figure (a), AC output appears intermittently at the 8 output terminals of the oscillator, and after rectification, the output at output terminal A has a large amount as shown in Figure 5 (b). Ripple r occurs. This unstable oscillation and ripple r become audio noise, and both have a problem in that they adversely affect the built-in receiving circuit and audio circuit.

The present invention solves these conventional problems, and prevents oscillation from becoming unstable even when the potential difference between input and output decreases, thereby preventing the generation of audio noise and reducing ripple. It is an object of the present invention to provide a DC step-up power supply device that can suppress the power to a small level and eliminate adverse effects on receiving circuits and audio circuits disposed in close proximity.

Means for Solving the Problems In order to achieve the above object, the present invention provides an AC output that oscillates when a voltage is applied from a DC input power source and boosts the DC from an intermediate tap provided in the secondary winding of a transformer for oscillation. an oscillating section that takes out the AC voltage, a rectifying section that rectifies the AC output generated at the intermediate tap, and an AC output of the oscillating section by rectifying the AC voltage generated at the intermediate tap and applying negative feedback to the oscillating section. The configuration includes a voltage setting section that sets the voltage to a predetermined level.

Therefore, according to the present invention, even when the potential difference between the input and the output becomes small, the oscillation is not made unstable, thereby preventing the generation of audio noise and suppressing the ripple to a small level.
It is possible to eliminate adverse effects on receiving circuits and audio circuits arranged in close proximity.

Embodiment FIG. 1 shows the structure of a DC step-up power supply device according to an embodiment of the present invention. In FIG. 1, 21 is a DC input power source. 22 is a capacitor for stabilizing the input power supply, and is connected in parallel to the input power supply 21.

23 is an oscillation transformer, one end of whose primary winding 23+ is grounded, and the other end connected to a resistor 24 and a capacitor 25.
It is connected to the base of the oscillation transistor 26 via. On the other hand, one end of the secondary winding 232 of the transformer 23 is connected to the positive electrode of the input power source 21, the other end is connected to the collector of the transistor 26, and has an intermediate tap 230.

27 is a resistor connected between the positive electrode of the input power source 21 and the base of the transistor 26, and the emitter of the transistor 26 is grounded. The transformer 23, the resistor 24, the capacitor 25, the transistor 26, and the resistor 27 constitute the oscillation section 101.

28 is a rectifying diode whose anode is connected to the collector of the transistor 26 and whose cathode is connected to the output terminal C of the DC booster power supply;
It is a smoothing capacitor with one end connected to the cathode of the diode 28 and the other end grounded. The diode 28 and the smoothing capacitor 29 constitute a rectifying section 102.

30 is a constant voltage diode whose cathode is connected to the cathode of the diode 28 to set a predetermined voltage; 31;
is a transistor whose base is connected to the anode of the voltage regulator diode 30, whose collector is connected to the base of the transistor 26, and whose emitter is grounded; and 32 is a transistor whose one end is connected to the base of the transistor 31. The voltage setting section 103 is constituted by a constant voltage diode 30, a transistor 31, and a resistor 32.

Next, the operation of the above embodiment will be explained. Input power supply 21
The voltage is applied to the base of the transistor 26 of the oscillation unit 101 via the resistor 27 and is
It is connected to the collector of the transistor 26 via the secondary winding 232, and the transistor 26 oscillates at a predetermined frequency determined by the time constant of the resistor 24 and capacitor 25, and induces an oscillation output in the secondary winding 232 of the transformer 23.

The secondary winding 232 of this transformer 23 has an intermediate tap 2.
30, and by the winding of this secondary winding 232,
The output voltage of the oscillation unit 101 at the point shown in FIG.

Further, at this time, when the output voltage of the oscillation unit 101 at point D in the intermediate tap 230 becomes equal to or higher than the zener voltage of the voltage regulator diode 30, the voltage regulator diode 30 becomes conductive, and a base current flows to the base of the transistor 31. .

As a result, the collector potential of the transistor 31 decreases, negative feedback is applied to the oscillation section, the base potential of the transistor 26 also decreases, and the oscillation output level of the transistor 26 returns to the predetermined set level.

As described above, according to the DC step-up power supply device according to the present embodiment, the level of negative feedback is lowered without lowering the level of the oscillation unit 101, and the negative feedback to the oscillation unit 101 is made appropriate.
Even when the difference between the input voltage and the output voltage becomes small, there is an effect that a stable DC boosted potential can be obtained without intermittent oscillation.

Effects of the Invention As is clear from the above embodiments, the present invention oscillates when a voltage is applied from a DC input power source and extracts an AC output obtained by boosting the DC from an intermediate tap provided in the secondary winding of an oscillation transformer. an oscillator; a rectifier that rectifies the AC output generated at the intermediate tap; and a rectifier that rectifies the AC voltage generated at the intermediate tap and applies negative feedback to the oscillator to adjust the AC output of the oscillator to a predetermined level. Since the configuration is equipped with a voltage setting section that sets the voltage, even when the potential difference between the input and output is small, the oscillation does not become unstable, thereby preventing the generation of audio noise and suppressing ripples to a small level. Therefore, it is possible to eliminate adverse effects on the receiving circuit and audio circuit that are arranged in close proximity.

[Brief explanation of drawings]

Figure 1 is a circuit diagram of a DC boost power supply according to an embodiment of the present invention, Figure 2 is a block diagram of a general DC boost power supply, Figure 3 is a circuit diagram of a conventional DC boost power supply, and Figure 4 is a circuit diagram of a conventional DC boost power supply. The figure is a waveform diagram showing the oscillation waveform and output waveform when the DC boost power supply shown in Figure 3 is oscillating or stable, and Figure 5 is a waveform diagram when the DC boost power supply shown in Figure 3 is oscillating intermittently. FIG. 2 is a waveform diagram showing an oscillation waveform and an output waveform of. 21...Input power supply, 23...Transformer, 230...
Intermediate tap, 101... oscillation section, 102 river rectification section, 1
03... Voltage setting section. Name of agent: Patent attorney Akira Koeji and two others Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 1Z A

Claims (1)

[Claims] An oscillation unit that oscillates when voltage is applied from a DC input power source and extracts an AC output obtained by boosting the DC from an intermediate tap provided in the secondary winding of the oscillation transformer, and a rectifier that rectifies the AC output generated at the intermediate tap. and a voltage setting unit that rectifies the AC voltage generated at the intermediate tap and applies negative feedback to the oscillation unit to set the AC output of the oscillation unit to a predetermined level.