JPH03243165A - Booster type power supply circuit - Google Patents

Abstract

PURPOSE:To prevent stepping out of synchronism and unusable picture, etc., of TV receivers, taperecorders and the like which occur when the power supply is switched on, by connecting a diode between DC supply voltage and an output terminal of a rectifier or a feed-back terminal of an oscillator. CONSTITUTION:When a power switch is turned on, a potential of a connection point a rises on a time t1. And a current is supplied to an output terminal B through a diode 14 from the connection point A. Therefore, a potential of the output terminal B rapidly rises and the current is supplied to a feed-back terminal 6c of a blocking oscillator 6 through an amplifier 13 from the output terminal B. And a rise time for an output voltage of the blocking oscillator 6 is reduced by a time (t2-t3) which is required to rise a power supply voltage VCC. This enables the supply of a specified voltage to a tuning circuit, electronic tuner and the like as soon as the power switch is turned on.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to a step-up power supply circuit for obtaining a DC voltage with a higher potential than a DC power supply voltage, and in particular to speed up the rise of the power supply voltage after the power is turned on. This invention relates to a step-up power supply circuit that can perform

[Prior Art] Televisions, videotape recorders, radios, wireless devices, etc. incorporate internal power supply circuits that rectify and smooth AC power to generate current and voltage. In order to maintain appropriate operating levels for each of the electronic circuits built into the system, the voltage is boosted by a power supply circuit that can boost the DC voltage without using a transformer.

FIG. 3 is a circuit diagram of a conventional step-up power supply circuit, which generates a voltage to be supplied to a television tuner selection circuit or an electronic tuner. Referring to the same figure, power supply V
cc is connected to a smoothing circuit 5 consisting of a capacitor 2, a capacitor 3, and a choke coil 4 via a power switch. A power terminal 6a of a blocking oscillator 6 is connected to a connection point A between the capacitor 3 and the choke coil 4. An oscillation coil 7 is connected between this power supply terminal 6a and an output terminal 6b of the blocking oscillator 6. A smoothing circuit 12 consisting of a capacitor 9, a capacitor 10, and a resistor 11 is connected to the output terminal 6a of the blocking oscillator 6 via a diode 8.

An amplifier 13 and a load such as a tuner selection circuit or an electronic tuner are connected to the output terminal B of the smoothing circuit 12. The output terminal of the amplifier 13 is connected to the feedback terminal 6C of the blocking oscillator 6.

The operation of the step-up power supply circuit will be explained based on the output characteristic diagram shown in FIG. First, when the power switch 1 is turned on at a point to, the power supply voltage Vcc is smoothed by the smoothing circuit 5. The voltage at connection point A at this time is capacitor 2.
3 and choke coil 4, and reaches approximately the specified voltage at time tl. The blocking oscillator 6 starts operating from the time when this specified voltage is reached, and outputs an oscillation output with a higher potential than the DC power supply voltage Vcc from the output terminal 6b. This oscillation output is half-rectified by the diode 8 and then smoothed by the smoothing circuit 12. The smoothed voltage is further applied to the feedback terminal 6C of the blocking oscillator 6 via the amplifier 13. This causes the blocking oscillator 6 to maintain a constant potential.

Here, the output characteristic of the output terminal B rises with a time constant determined by the capacitors 9 and 10 and the resistor 11 of the smoothing circuit 12, and reaches a substantially specified potential at time t2.

[Problems to be Solved by the Invention] However, in video tape recorders and televisions, the output voltage of the step-up power supply circuit is used as the power supply voltage of the tuner selection circuit and electronic tuner, so the output terminal B is output from the time the power switch 1 is turned on. Regular tuner selection is not performed until the voltage reaches the specified voltage. Therefore, a normal image is not displayed until tOt2 (several tens of milliseconds), resulting in an unsightly image with noise and disturbed synchronization. This problem with tuner selection occurs not only in televisions and video tape recorders, but also in electronic devices such as radios and wireless devices that use tuners.

The present invention has been made in view of the above-mentioned problems, and provides a step-up power supply circuit that can suppress synchronization disturbances and unsightly images of televisions, tape recorders, etc. when the power is turned on. The purpose is to

[Means for Solving the Problems] A step-up power supply circuit of the present invention for achieving the above object has the following features:
An oscillating means that oscillates at a potential higher than the DC power supply voltage in response to a feedback current, a rectifying means that rectifies the oscillation output of the oscillating means, and a connection between the output terminal of the rectifying means and the feedback terminal of the long-term oscillating means. and a diode connected between the DC power supply and the output terminal of the rectifying means or the feedback terminal of the oscillating means.

[Operation of the Invention] According to the present invention having the above configuration, the potential of the output terminal is increased by the power supply voltage due to the diode being connected between the DC power supply voltage and the output terminal of the rectifying means or the feedback terminal of the oscillation means. The increased potential of the output terminal is applied to the oscillation means via the feedback means. Therefore, the oscillation means can quickly output an oscillation output at a specified potential. By rectifying this oscillation output by the rectifier, a specified voltage can be applied to the subsequent load.

[Example] A step-up power supply circuit of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 is a circuit diagram showing an embodiment of the present invention. The only difference in the circuit configuration is the diode 4, which includes a power switch 1, a capacitor 2.3, a choke coil 4, a smoothing circuit 5, a blocking oscillator 6, an oscillation coil 7, a diode 8, a capacitor 9, 10, a resistor 11, The same symbol is used for smoothing circuit 2 and amplifier 3.

Referring to the figure, an anode of a diode 14 is connected to a connection point A between a capacitor 3 and a choke coil 4, and a cathode of the diode 14 is connected to an output terminal B.

The operation of the step-up power supply circuit shown in FIG. 1 will be explained with reference to FIG. 2. When the power switch is turned on, the potential at the connection point A rises at time tl. Then, a current is supplied from the connection point A to the output terminal B through the diode 14. Therefore, the potential at the output terminal B rises rapidly and is supplied from the output terminal B to the feedback terminal 6C of the blocking oscillator 6 via the amplifier 13. The blocking oscillator 6 increases the voltage of the oscillation output until the voltage supplied to the feedback terminal 6c reaches a specified potential. Thereby, the rise time of the output voltage of the blocking oscillator 6 is shortened (t2-t3) until it rises by the amount of the power supply voltage Vce.

Therefore, immediately after turning on the power switch, output terminal B is
A specified voltage can be supplied to the tuner selection circuit, electronic tuner, etc. connected to the tuner, and it is possible to suppress synchronization disturbances and unsightly images.

[Effects of the Invention] According to the present invention as described above, by applying a DC voltage to the output terminal of the rectifying means through a diode, the rise of the power supply voltage applied to the load can be made faster than in the conventional case. Therefore, it is possible to achieve the effect that the start-up of electronic components incorporated in televisions, tape recorders, radios, wireless devices, etc. can be made faster.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing an embodiment of the present invention, Fig. 2 is a graph showing the output characteristics of the present invention, Fig. 3 is a circuit diagram of a conventional step-up power supply circuit, and Fig. 4 is the same as Fig. 3. It is an output characteristic diagram. In the figure, 6 is a blocking oscillator, 7 is an oscillation coil,
8 is a diode as a rectifier, 13 is an amplifier, 14
is a diode.

Claims (1)

[Claims] Oscillating means that oscillates at a potential higher than the DC power supply voltage in response to a feedback current, rectifying means that rectifies the oscillation output of this oscillating means, and an output terminal of this rectifying means and feedback of the oscillating means. A step-up power supply circuit comprising: a feedback means connected between the DC power supply terminal and the output terminal of the rectification means or a feedback terminal of the oscillation means.