JPH028517Y2 - - Google Patents

Description

[Detailed description of the invention] This invention is a power supply for an electronic device that has a part to which DC power is constantly supplied, and the supply of DC power to the remaining parts can be controlled by signals from this part. Regarding the configuration of the circuit.

An example of such an electronic device is a video recorder with a built-in timer, and the relationship between its power supply circuit and load is constructed as shown in the block diagram of FIG. Load 1, which is a timer, is always supplied with DC power from the power supply circuit 3.
The switch 4 is operated by the signal, and power is supplied to the load 2, which is the driving part of the original video recorder. In the absence of a signal from load 1, no power is supplied to load 2.

FIG. 2 shows a circuit diagram of a conventional example of such a power supply circuit. Only a portion of the output side of the power supply circuit 3 is shown, and the DC power obtained across the capacitor C3 provided to reduce the output impedance is applied to the load 1 and the load 2 via the switch section 5. Supplied. Load 1 and load 2 are each equivalently represented by a parallel circuit consisting of a resistor and a capacitor provided in the load itself to obtain a stable DC voltage. When the contacts of the switch portion 5 are open, DC power is supplied to the load 1, and when the contacts are closed by a signal from the load 1, DC power is also supplied to the load 2. However, in such a circuit configuration, when the contact of the switch portion 5 is closed, the capacitor C3 and the capacitor C2 of the load 2 are connected in parallel. Since the load 2 is a driving part of the video recorder, the capacitance value of the capacitor C2 provided in the load itself is usually larger than that of the capacitor C3. Therefore, a large current with little restriction flows transiently from the capacitor C3 to the uncharged capacitor C2 through the contacts of the switch section 5. This not only heats up the contacts of the switch part 5;

Since the terminal voltage of capacitor C3 is divided by capacitor C2 and lowered, and both capacitors are charged by the current limited by the power supply circuit 3 standard, a state in which the terminal voltage significantly drops for a certain period of time occurs. This adversely affects the continuous operation of the load 1 and causes malfunctions.

The present invention is designed to replace conventional switches in power supply circuits of electronic devices such as video recorders, when DC power is supplied to a relatively large load by controlling a relatively small load that is constantly connected to the power supply circuit. To prevent and protect contacts from heating caused by large currents flowing transiently through parts, and to prevent and protect terminal voltages divided by capacitors in power supply circuits and capacitors in large loads from temporarily dropping. The main purpose is to prevent malfunctions of small loads caused by this.

The present invention is a power supply circuit for an electronic device to which multiple loads are connected, and it consists of a capacitor and a diode that serves to prevent the discharge of the capacitor between the high-potential side and low-potential side power lines from which DC power is supplied to the loads. At the same time, a first load with a control switch is connected to both ends of the capacitor, and a first load is connected to both ends of the series circuit, so that only the first load receives direct current. an OFF state where power is supplied, a second load is connected to both ends of the series circuit, and a first load is connected to both ends of the capacitor at the same time, and DC power is supplied to both the first load and the second load. The present invention is characterized in that it is provided with a switch section for switching the on state, and that switching from the off state to the on state is performed by a signal from a first load control switch applied to the switch section.

The following description will be made with reference to FIG. 3, which is a circuit diagram showing an embodiment of the power supply circuit according to the present invention. Note that the same parts as in FIGS. 1 and 2 are given the same reference numerals.

In FIG. 3, the power supply circuit 6 for supplying DC power, the load 1, the load 2, and the switch section 7 are all shown surrounded by dashed lines.

The power supply circuit 6 uses a switching method, and includes a control transistor Q and a control transistor Q.
Only the flywheel diode D1, the choke coil L, and the series circuit of the capacitor C3 and the diode D2 on the output side are shown, and other circuit parts are omitted, including the circuit part that drives the control transistor Q. . T1 and T4 are output terminals on the high potential side, and T2 is an output terminal on the low potential side.

DC power is obtained at both ends of a series circuit of capacitor C3 and diode D2, the anode of diode D2 is connected to a high potential power line, and one end of capacitor C3 is connected to a low potential power line. The capacitor C3 is provided to reduce the output impedance of the power supply circuit 6, and the diode D2 prevents the capacitor C3 from rapidly discharging transiently when DC power is supplied to the load 2, as described later. do.

The switch part 7 is composed of a transfer type relay, and P1 is a contact on the break side.
P2 is a make side contact. The switch part 7 is attached to the output side end of the power supply circuit 6, and the transfer contact P3 is connected to the high potential side power supply line, and the break side contact P1 is connected to the connection point between the diode D2 and the capacitor C3. Connected to output terminal T4. Also, the make side contact P2 is connected to the output terminal T1.

A load 1, which is a timer, is equivalently represented by a parallel circuit of a resistor R1 and a capacitor C1, and is further provided with a timer control switch S1. And load 1 is connected between output terminals T2 and T4,
The control switch S1 is connected via a terminal T3 of the power supply circuit 6 to a coil of a transfer type relay constituting the switch section 7. Load 2, which is the driving part of the video recorder, is resistor R2 and capacitor C2.
It is equivalently represented by a parallel circuit of , and the output terminal T
2, connected between T1. Load 1 capacitor C
1. Capacitor C2 of load 2 is an input capacitor provided in the load itself so that a stable DC voltage is supplied to each load.

The features of the power supply circuit of the present invention configured as described above will be explained next. When the break side contact P1 of the switch part 7 is closed as shown in Fig. 3, the load 1
is connected to both ends of a series circuit of capacitor C3 and diode D2 and to both ends of capacitor C3 via output terminals T4 and T2, and DC power is supplied from both ends of the series circuit. And no DC power is supplied to the load 2.

When the control switch S1 of the load 1 is closed and a current as a signal flows through the coil of the switch portion 7 and the make side contact P2 is closed, the load 2 is connected to the output terminal T.
1. Capacitor C3 and diode D via T2
It is connected to two series circuits and DC power is supplied.
On the other hand, load 1 is connected to both ends of capacitor C3 via output terminals T4 and T2, and is supplied with DC power.

When the make side contact P2 closes, it connects the uncharged capacitor C2, so the DC voltage drops significantly across the series circuit of the output side diode D2 and capacitor C3, but the capacitor C3 is connected to the reverse biased diode D2. capacitor C to be connected to capacitor C2 via
3, the transient rapid discharge does not occur. The capacitor C2 is charged with a current determined by the specifications of the power supply circuit 6, and the DC voltage between the output terminals T1 and T2 reaches a normal value, and the load 2 is driven. In this embodiment, a capacitor C3 is provided on the output side to reduce the output impedance of the power supply circuit 6 even when DC power is supplied to the load 2.
Since no transient discharge occurs as in the conventional case, there is no fear that the make side contact P2 of the switch portion 7 will be heated and damaged. Furthermore, since the terminal voltage of the capacitor C3 does not drop, the load 1 is supplied with a DC voltage substantially the same as that at both ends of the series circuit of the capacitor C3 and the diode D2. Therefore, fluctuations in the DC voltage supplied to the load 1 will not cause malfunctions. Note that when the control switch S1 of the load 1 is opened and the make side contact P2 of the switch part 7 is opened, the potential of the transfer contact P3 rises so as to release the magnetic flux energy of the choke coil L of the power supply circuit 6, but the diode D2 is Since current flows through the capacitor C3 and the increase in potential is limited, the make side contact P2 will not heat up.

As described above, in the power supply circuit of the present invention, a capacitor and a series circuit that serves to prevent discharge of the capacitor are connected between the high-potential side and low-potential side power lines from which DC power is supplied to the load. can be,
DC power can be simultaneously supplied to a relatively large load from both ends of the capacitor, and to a small load from both ends of the capacitor. Therefore, even when direct current power is supplied to a large load using a signal from a control switch for a small load, transient discharge of the capacitor does not occur, so that heating of the switch portion can be prevented and protected. Furthermore, since the terminal voltage of the capacitor does not drop, a small load will not cause malfunction.

The power supply circuit of the present invention has a wide range of applications without being limited to the embodiments.

Although the load 1 and the load 2 have been described as driving parts of a timer and a video recorder, respectively, it is clear that they can be used in various electronic devices based on the technical idea of the present invention.

Further, although a transfer type relay is used for the switch portion 7, it can also be configured using a transistor. In that case, it can be constructed using transistors with small power capacity, and the reliability of the power supply circuit is improved. None of these depart from the scope of the present invention.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing the relationship between a power supply circuit and a load to which the present invention relates, Fig. 2 is a circuit diagram of a conventional power supply circuit, and Fig. 3 shows an embodiment of the power supply circuit of the present invention. It is a circuit diagram. 1, 2: load, 3, 6: power supply circuit that supplies DC power, 5, 7: switch section, S1: control switch, T1, T2, T4: output terminal, T3: terminal.

Claims (1)

[Scope of utility model registration request] In a power supply circuit of an electronic device in which the DC power supply state of a second load having an internal input capacitor is controlled by a first load, a high potential side and a low potential side from which DC power to be supplied to the load can be obtained. A series circuit consisting of a capacitor and a diode that prevents its discharge is connected between the power lines of the
A first capacitor with a control switch is located at both ends of the capacitor.
A load is connected to both ends of the series circuit, and a first load is connected to both ends of the series circuit to supply DC power only to the first load, and a second load is connected to both ends of the series circuit. A first load is connected to both ends of the capacitor at the same time, and a switch part is attached that switches the on state to supply DC power to both the first load and the second load, and switches from the off state to the on state. 1. A power supply circuit characterized in that: is performed by a signal from a first load control switch applied to the switch section.