JPS6053550B2 - capacitor charging circuit - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a capacitor charging circuit, and particularly to a demagnetizing device,
The present invention relates to a capacitor charging circuit suitable for driving a spark discharge type ignition device, etc.

2. Description of the Related Art Electrical and electronic devices that utilize electrical transient phenomena that occur when a capacitor is charged and the charged charge is discharged once or several times are used in various fields.

In this case, the charging charge is given by the product of the voltage applied to the capacitor and the capacitor's own capacitance, so it is desirable that the charging voltage be somewhat high in order to obtain the amount of charge necessary for the load device to be driven. . By the way, when a battery is used as a power source, the terminal voltage of the battery is generally insufficient, and it is necessary to boost the voltage. Further, it is also necessary to take some measures to avoid fluctuations in the charging voltage due to battery consumption and the like and to stabilize the amount of charged charge. Furthermore, it is desirable to take voltage stabilization measures not only when using batteries but also when boosting a low voltage source. In view of the above-mentioned points, the present invention aims to provide a capacitor charging circuit capable of boosting the power supply voltage of a battery or the like and charging the capacitor to a constant amount of charge.

Embodiments in which the capacitor charging circuit according to the present invention is applied to a degaussing device will be described below with reference to the drawings.

In FIG. 1, a battery 1 serving as a power source is connected to a ■-■ converter 3 via a switch 2.

This ■-■ converter 3 has a transistor oscillation circuit including a transistor Q1, and the output of this oscillation circuit is rectified by a diode D1, smoothed by a capacitor C1, and a boosted voltage is supplied to the switch circuit 4. This switch circuit 4 includes a transistor Q2 and a transistor Q2 that supply the output of the -X converter 3 to a charging capacitor C2.
a voltage regulator diode D2 connected to the emitter of the transistor Q2 to detect whether or not the charging voltage has reached a desired value; and a transistor that operates when the voltage regulator diode D2 breaks over to control the base current of the transistor Q2. Q3, and these constitute a series control type constant voltage circuit with the capacitor C2 as a load. Furthermore, a light emitting diode D3 is connected to the collector side of the transistor Q2.
A series circuit consisting of a transistor Q4 and a transistor Q4 is provided, and the transistor Q4 forms a positive feedback loop with the transistor Q3. That is, both transistors Q3 and Q4
constitutes a flip-flop as a state holding circuit. The transistor Q5 and the transistor q included in the control circuit for lowering the output of the DC-DC converter 3 are controlled to be turned on or off by the collector outputs of the transistors Q3 and Q4, respectively. Now, a demagnetizing oscillation circuit 5 driven by the charge of the capacitor C2 is connected to the charging capacitor C2 via a transistor q.

This degaussing oscillation circuit 5 uses the winding of a degaussing electromagnet M as a load, and consists of a capacitor-coupled multivibrator including transistors Q7 and Q8, and the degaussing electromagnet M is brought close to a magnetic body such as a magnetic head to be demagnetized. By operating the magnet, the magnetic material is demagnetized. In the above configuration, when the switch 2 is closed, the voltage across the capacitor C2 is very small, so the constant voltage diode D2 is in a cutoff state, and therefore the transistors Q3Q4, Q, Q6 are also in a cutoff state.

Therefore, the light emitting diode D3 does not light up, and the degaussing oscillation circuit 5 is disconnected from the capacitor C2.
The X-■ converter 3 is in the maximum output state. Therefore,
Immediately after the switch 2 is closed, the terminal voltage of the battery 1 is boosted by the DC-DC converter 3 in the maximum output state, and is applied to the charging capacitor C2 via the forward bias transistor Q2. As a result, the voltage of capacitor C2 is
It rises as shown by dotted line A. When the voltage of the capacitor C2 reaches approximately the sum of the zener voltage of the voltage regulator diode D2 and the rising voltage between the base and emitter of the transistor q, the transistor Q3 is biased in its active region through the voltage regulator diode D2. . Due to this negative feedback effect of transistor q, transistor Q
The emitter voltage of C2 is controlled to a constant voltage, and the emitter voltage of capacitor C2
Charging ends. Then, the load on the DC-DC converter 3 becomes lighter, so D
The output voltage of the C-DC converter 3 rises further faster than in the previous state. Then, the output voltage of the ■-■ converter 3 is the charging end voltage of the capacitor C2 (setting voltage of the constant voltage circuit), the voltage between the base and emitter of the transistor Q2, the voltage between the base and emitter of the transistor "q", and the voltage between the base and emitter of the transistor "q". When the voltage equal to the rising voltage of diode D2 is reached, transistor Q4 becomes conductive, and this collector current further forward biases transistor Q3, so that the collector current of transistor Q3 increases.This collector current The increase in Q4 also performs a positive feedback effect that forward biases the base of transistor Q4, so that transistors Q3 and q are instantaneously driven to the saturation region. In this state, transistor Q2 is cut off, and transistor 9 is turned off. Therefore, the charge stored in the charging capacitor C2 is supplied to the demagnetizing oscillation circuit 5. Since the demagnetizing oscillating circuit 5 performs an oscillating operation while consuming the charge amount of the capacitor C2, the demagnetizing electromagnet As shown in Figure 2B, the excitation current flowing through the winding of M has a waveform that initially has a large amplitude and whose amplitude decays exponentially over time.In other words, the demagnetizing electromagnet M initially Since it generates an alternating magnetic field that is sufficiently strong and attenuates over time, it demagnetizes the magnetic material in the vicinity of the degaussing electromagnet M.The light emitting diode D3 is activated when the transistor Q4 becomes conductive. That is, as shown in FIG. 2C, the light is turned on at the same time as the degaussing oscillation circuit 5 starts operating.

Furthermore, at the same time, the transistor Q6 is biased in the forward direction, and the output of the converter 3 is lowered by the transistor q, and is controlled to a voltage suitable for lighting the light emitting diode D3. As a result, as shown in FIG. 2D, the current consumption of the battery 1 is significantly reduced after charging the charging capacitor C2. As a result, unnecessary consumption of the battery 1 is reduced. Strictly speaking, the light-emitting diode D3 lights up when degaussing starts, but since degaussing takes a fraction of a second, when viewed visually, the light-emitting diode D3 does not indicate the completion of degaussing. You can also think that. When the switch 2 is opened after degaussing is completed, each transistor etc. is reset to its original state. Note that it is possible to reset by lowering the base voltage of the transistor O. As explained above, according to the above embodiment, the charging capacitor C2 can always be charged to a constant voltage regardless of changes in the terminal voltage of the battery 1. Therefore, a demagnetizing magnetic field of the same strength can always be obtained as the output of the demagnetizing oscillation circuit 5. Furthermore, after the charging capacitor C2 is charged, the output of the DC-DC converter 3 is reduced, thereby reducing the power consumption of the battery 1. Furthermore, since the light emitting diode D3 does not light up, it is possible to indicate that the degaussing operation is not possible at the end of the battery life, which is easy and convenient to use. FIG. 3 shows another embodiment of the invention.

In this figure, battery 1 is connected to DC-D via switch 2.
The voltage boosted here is applied to the charging capacitor C2 via the switch circuit 4A, and the demagnetizing oscillation circuit 5 is driven by the charged charge of the charging capacitor C2. There is. Here, D
The configuration of the C-■ converter 3 and the degaussing oscillation circuit 5 is as follows.
This embodiment is the same as the embodiment shown in the figure, but the configuration of the switch circuit 4A is different. That is, a constant voltage diode D2 is connected to the collector side of the transistor Q2 that supplies the output of the DC-DC converter 3 to the charging capacitor C2, and this diode D2 allows the voltage on the collector side of the transistor Q2 to reach a predetermined value. It is designed to detect whether or not.
The configurations of the other transistors Q3 to Q6 are the same as in FIG. In the above configuration, when the switch 2 is closed, the terminal voltage of the battery 1 is boosted by the DC-DC converter 3 in the maximum output state, and is applied to the charging capacitor C2 via the forward bias transistors.

As a result, the voltage of capacitor C2 increases as shown by the dotted line x in FIG. 4A. When the output voltage of the DC-DC converter 3 reaches approximately the sum of the zener voltage of the voltage regulator diode D2 and the rising voltage between the base and emitter of the transistors, the transistor (is forward biased through the voltage regulator diode D2). conduction.
Since the transistors Q3 and Q4 constitute a positive feedback loop, both transistors are instantaneously excited to the saturation region. As a result, the transistor Q2 is cut off, the transistors Q5 and Q6 are turned on, and the output of the ■-■ converter 3 is changed to the capacitor C2, as shown by the solid line Y in FIG.
It is lowered after being separated from the At the same time, the charge stored in the capacitor C2 is supplied to the demagnetizing oscillation circuit 5, and the excitation current flowing through the winding of the demagnetizing electromagnet M is as shown in FIG.
It becomes as shown in . Further, the light emitting diode D3 is turned on after the transistor Q4 becomes conductive as shown in FIG. Furthermore, as a result of controlling the output of the DC-DC converter 3 by the transistor Q6, the current consumption of the current 1 is significantly reduced after charging the charging capacitor C2, as shown in FIG. 4D. As explained above, in this embodiment, the voltage regulator diode D2 detects that the output of the converter 3 reaches a predetermined value, but the voltage drop across the transistor Q2 during charging is small. Therefore, the charging capacitor C2 can be charged to a substantially constant voltage.

As a result, substantially the same effect as the embodiment shown in FIG. 1 can be achieved. In each of the above embodiments, a degaussing device in which a degaussing oscillation circuit 5 is connected as a load of a charging capacitor C2 has been explained as an example, but various devices such as a high-voltage discharge circuit having a high-voltage transformer as a load are also applicable. It is clear that the connection is possible.

Furthermore, in the switch circuit, various changes can be made to the connections and configurations of display elements and switching elements. As described above, according to the present invention, there is obtained a capacitor charging circuit that can charge the capacitor to a constant amount of charge by boosting the voltage of a power source such as a battery.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment in which a capacitor charging circuit according to the present invention is applied to a degaussing device, FIGS. 2A to D are waveform diagrams showing its operation, and FIG. 3 is another embodiment of the present invention. A circuit diagram showing an example, and FIGS. 4A to 4D are waveform diagrams showing the effect thereof. DESCRIPTION OF SYMBOLS 1... Battery, 2... Switch, 3... ■-■ converter, 4... Switch circuit, 5... Oscillator circuit for degaussing, C2... Capacitor for charging, D2... Constant Voltage diode, D3... Light emitting diode, Q1 to Q8.
...Transistor, M...Demagnetizing electromagnet.

Claims (1)

[Claims] 1. In a capacitor charging circuit that boosts battery voltage with a DC-DC converter and charges a capacitor via a switch circuit, the switch circuit includes a first switching element that connects the DC-DC converter and the capacitor; a second switching element that connects the capacitor and the load; a control circuit that reduces the output of the DC-DC converter; and a voltage detection element that operates when the voltage of the DC-DC converter or the capacitor reaches a predetermined value. and two transistors connected to each other to form a positive feedback loop, and in a reset state, the first switching element is kept in a conductive state and the second switching element is kept in a cut-off state. , comprising a state holding circuit that turns off the first switching element and turns on the second switching element in a set state, and a display element that operates in accordance with the set state of the holding circuit. , the state holding circuit is set by the operation of the voltage detecting element to turn off the first switching element which has been in a conductive state, maintain the second switching element in a conductive state, and at the same time cause the control circuit to Said DC
- A capacitor charging circuit characterized in that it reduces the output of a DC converter.