JPS61234411A - Power supply circuit - Google Patents

Abstract

PURPOSE:To reduce the power consumption of a power supply circuit by inserting a switch circuit turned on when one voltage reaches a prescribed value or below between voltage lines of different constant voltage power supply circuits. CONSTITUTION:A transistor (TR) Q3 is a switch power TR, which is controlled by a voltage comparator circuit comprising resistors R1, R2 and a constant voltage diode D1. When a voltage V1 is lowered to a prescribed value or below after the diode D1 is selected, the TR Q3 is turned on to compensate an unregulated voltage of a low voltage measurement voltage power supply circuit. A voltage V2 is compensated completely to a reduced voltage E1 through the said compensation at normal reproduction so as to stabilize the voltage V2. Since the voltage E2 can be lowered, power saving is attained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a power supply circuit used in video disk players, video tape recorders (VTRs), and the like.

2. Description of the Related Art Video disc players, VTRs, and the like generally use commercial power. These devices are generally equipped with two or more DC constant voltage power supply circuits with different voltages, but 1
1. For example, the current consumption of the circuit differs depending on the usage mode of the device, such as ``ζ standby'', ``1 stop'', ``playback'', ``recording'', and ``retrieval''.

On the other hand, when using a commercial power source, two of the power source fluctuation factors, voltage fluctuation countermeasures and instantaneous power outage countermeasures, must be satisfied, and when designing a power supply circuit, each voltage must be at its maximum under the worst input conditions. In the case of loads, guarantees were required, creating challenges for power saving and cost reduction.

The conventional example will be explained below with reference to FIG.

FIG. 2 shows a DC constant voltage power supply circuit widely used in video disk players and VTRs. AC power E1 is supplied from a commercial power source, and is connected to 2 by power transformer 1.
The AC voltages E'2 and E'3 are converted into two AC voltages E'2 and E'3, which are rectified by rectifier circuits 2 and 3, and stabilized voltages v3 and v2 are generated by two DC stabilized power supply circuits 4 and 5 with different voltages. . Typical voltages are +12V for v3 and +5V for V2. The stabilized voltage v3 on the high voltage side is normally supplied to the audio circuit and the motor control circuit, and the stabilized voltage v2 on the low voltage side is normally supplied to the microcomputer system.

Therefore, the highly stabilized voltage v3 often has a large load fluctuation depending on the mode of the device, and the low voltage v3 often has little variation.

On the other hand, the voltage fluctuation of commercial power supply is ±10%, allowing for a margin of ±16%, and that of momentary power outage is -26%.

Approximately 200 milliseconds must be considered.

In particular, since the low stabilized voltage v2 in the figure is supplied to the microcomputer, sufficient stabilization is required.

Therefore, in the conventional circuit, the rectified voltage v' is set so that v2 and v3 can be stabilized even when El is about -25%.
1 and V'4.

Problems to be Solved by the Invention However, in the conventional configuration, due to the table voltage design as described above, v'1 and V'4 become high when used at normal voltage.
The loss power consumption of each constant voltage circuit is large, and the transistor Q
1 and Q2 generate a lot of heat, so a large-capacity heat sink was required. Since the magnifications E'2 and E'3 become high, the efficiency of the entire power supply circuit decreases and costs increase.

The present invention has been developed in view of the above-mentioned problems, and in order to achieve the above object, the present invention has been developed to turn on voltage lines of different constant-voltage power supply circuits when the voltage of one of them falls below a certain value. The present invention is characterized in that a switch circuit is inserted to perform link control of the two different voltage power supplies described above.

Function: This configuration reduces the power consumption of the low voltage side voltage stabilization circuit during normal operation, and also transfers the high voltage side stabilized output voltage to the low voltage side line when the voltage of the commercial power supply drops. By supplying this, it is possible to achieve voltage stabilization on the low voltage side of devices such as microcomputers that are highly dependent on the power supply voltage. The switch circuit operates to turn on when the voltage on the low voltage side falls below a certain value.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to FIG.

In the figure, 1 is a power transformer, 2 and 3 are rectifier circuits, and 4
6 is a stabilized power supply circuit on the low voltage side, and 6 is a stabilized power supply circuit on the high voltage side. Further, Ql and Q2 are voltage control transistors of respective constant voltage circuits.

Also Q3. R1, DI, and R2 are transistors constituting a switch circuit featured in the present invention.

Connect the emitter of transistor Q3 to the high-voltage stabilized voltage output terminal using a resistor and a constant voltage diode, connect the anode of constant voltage diode D1 to the low-voltage side through resistor R2, and directly connect the collector of transistor Q3 to the low-voltage side. Connected to the unregulated voltage terminal.

"', -J A power supply circuit as shown in Fig. 1 is used in a video disk player. Rectifying circuit 3. Stabilizing power supply circuit 5゜Voltage control transistor 02. Constant voltage on the high voltage side consisting of capacitor C2 and resistor r2. The output v3 of the power supply circuit is set to +12V, and the rectifier circuit 2. Stabilization power supply circuit 4. Voltage control transistor Q1
, a capacitor C1, and a resistor r1, the output v2 of the constant voltage power supply circuit on the low voltage side is set to +5V.

The voltage v2 is supplied to the microcomputer and logic circuit, and the current changes little depending on the usage mode of the video disc player, and the voltage 11 is about 700 mA.

V3 is supplied to audio, video, and control circuits, and the motor control circuit in particular has large fluctuations in current consumption. In particular, the turntable motor alone requires about 800 mA when starting and stopping, but 100 mA during steady rotation.
It is about mA. Therefore, the current I including that of other circuits
2 varies greatly depending on the usage mode of the video disc player, ranging from about 300 mA in normal playback mode to 10,100 O at peak time.

When considering the performance as a power source for a video disc player, the V2 must be most stable in normal playback mode, and the start and stop periods of the turntable motor are very limited and short. At the same time, if there is a major drop in commercial power such as a momentary power outage within this very limited short time, the microcomputer and other logic circuits will be reset and the player will return to its initial mode. is not a problem in practice.

If I2 during normal playback mode is about 300 fiA, there is a current margin of about 700 mA against the peak load.

Here, since the voltage drop of voltage control transistors Q1 and Q2 is 0.5 V or less of vCE8at of the transistors, V2. In order to stabilize voltages V1 and V3, unregulated voltages v1 and v4 must be maintained at +6.6V and +12.55V, respectively. However, as in the case of a momentary power outage, E
In the conventional circuit (FIG. 2) which attempts to guarantee these v'1 and V'4 up to 125%, the power loss during normal reproduction is large.

Therefore, in Fig. 1, R2 is kept lower than E'2 in Fig. 2, vl in Fig. 1 is kept lower than v'1 in Fig. 2, and El is about -1.
Set so that vl is 6.6v at 2%.

On the other hand, R3 and v4 in FIG. 1 are E'3 and v' in FIG.
Set to the same specifications as 4.

Transistor Q3 is a power transistor for switching, and is controlled by a voltage comparator circuit including resistors R1, R2, and a constant voltage diode D1.

In FIG. 1, v3 is +12V, and since step 1 is almost constant, vl changes according to changes in El.

Here, select the value of the constant voltage diode D1 so that vl is +6
．． When the voltage drops below 5V, transistor Q3 is turned on,
Reinforce unregulated voltage of low voltage measurement voltage power supply circuit.

With this reinforcement, v2 is completely guaranteed against voltage reduction of El during normal playback, and even when the turntable is started and stopped, it is possible to ensure the stability of v2 even at the expense of stabilizing v3 to some extent.

Furthermore, as mentioned above, since the voltage of <R2 can be lowered, power saving can be achieved.

For example, in a capacitive video disk player, the load on the high voltage side is large, the load on the low voltage side is constant, and the load on the high voltage side decreases during normal playback. It is extremely effective for power supply circuits of devices with an output of -4-12V and a low voltage measurement voltage output of +6V, and it was possible to lower the winding voltage E2 in FIG. 1 by about 13% compared to FIG. 2.

In addition, as the configuration of the switch circuit, the resistors R2 and
There is also a method of connecting the constant voltage diode D1 to the collector side of the transistor Q1.

Effects of the Invention As described above, according to the present invention, power consumption can be reduced and the most important feature can be achieved in power supply circuits having a plurality of DC stabilized power supplies, not only in the case of video disc players but also in other video equipment such as VTRs. Can reinforce constant voltage power supply,
Its practical effects are significant.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a power supply circuit in an embodiment of the present invention,
FIG. 2 is a circuit diagram of a prior art example. 1...Power transformer, 2, 3...Rectifier circuit, 4.6...Stabilized power supply circuit, Ql, Q2
... Constant voltage control transistor, Q3...
- Switch transistor, Dl... Constant voltage diode for voltage detection.

Claims (2)

[Claims] (1) Equipped with a power transformer that generates multiple AC voltages of different voltages from a commercial power supply, a rectifier circuit that rectifies each of the multiple AC voltages, and a constant voltage power supply circuit that stabilizes each of the output voltages. , a power supply circuit in which a switch circuit is inserted at least at one location between different voltage lines of the constant voltage power supply circuit. (2) The secondary winding of the power transformer is configured so that the low voltage winding is more vulnerable to voltage reduction in the primary winding than the high voltage winding, and the high voltage A switch circuit is inserted between the stable voltage line of the constant voltage power supply circuit on the side and the unregulated voltage of the constant voltage power supply circuit on the low voltage side, and when the unregulated voltage on the low voltage side drops below the normal voltage, The power supply circuit according to claim 1, characterized in that the switch circuit is made conductive.