JPH02261205A - Constant voltage power supply circuit for amplifier - Google Patents

Abstract

PURPOSE:To reduce the cost by feeding back a fluctuation of a voltage amplifier circuit in opposite phase. CONSTITUTION:When a plus input Va of an operational amplifier circuit is kept constant, a minus input terminal VNF remains at the same level. The output of the operational amplifier keeps the VNF constant with opposite phase operation of a transistor(TR) Q1. Moreover, the input Va and VNF are designed so as to have the same VCC characteristic (NF pin voltage versus Vcc characteristic) as the VF pin voltage when a capacitor is in use. Thus, even when the Vcc varies, the center point of the output is kept at the ideal voltage (simultaneously clipping voltage). Thus, the product cost is reduced and the required space around a power IC is reduced for the product and the dispersion in the characteristic of the IC due to the feedback pin capacity is eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION <Field of Industrial Application> The present invention relates to the configuration of a constant voltage circuit used before a power amplifier used before a speaker or the like.

<Prior Art> As a conventional constant voltage circuit, a DC coupling capacitor of 22 to 220 μF is externally attached, and filtering is performed using this to form a constant voltage circuit.

<Problems to be Solved by the Invention> However, in the conventional external capacitor, since the capacitor has a large capacity, it occupies a large area when mounted, and there are also problems in terms of cost.

Furthermore, the performance of capacitors is generally relatively variable, which may even affect the characteristics of the amplifier. Furthermore, a power amplifier does not operate unless the feedback bin voltage reaches a certain level, so if there is a capacitance on the feedback pin, it takes time to charge it, which slows down the startup time of the power amplifier.

The present invention aims to provide an amplifier power supply constant voltage circuit that does not suffer from the above-mentioned problems.

<Means for Solving the Problems> In order to solve the above-mentioned problems, a structure shown in the claims is used in which the idea of a compensation circuit, which has already been considered for constant current circuits, is applied to constant voltage circuits.

<Function> Since the present invention has the above-mentioned configuration, it can be integrated into an IC without an external capacitor, and can be used together with other circuits, which not only saves space but also reduces startup time. It operates instantly without any trouble.

<Example> An embodiment of the present invention will be described in detail using a circuit diagram.

FIG. 1 is a circuit diagram showing an embodiment of the present invention.

By making the voltage (Va) of the differential amplifier circuit constant voltage, one input terminal (VNF) is made to have the same potential.

The output of the differential amplifier operates with Ql in the opposite phase to its fluctuation, and VN
F is kept constant, and Va and VNF are designed to have the same vCC characteristics (NF pin voltage vs. Vcc characteristics) as the NF pin voltage when using a capacitor. Therefore, even if Vcc changes, the output midpoint is set to an ideal voltage (voltage that clips at the same time).

,:tL-VCC=13.2v RL=4Q r・
The data under the condition of IKHz are shown below.

Further, FIG. 2 shows waveforms comparing the conventional waveform and the present invention at this time. Figure 2 shows the conventional waveform at the SP end when starting up the amplifier (
The waveform of the output pin is shown in FIG. 2 ([1), and the waveform of the SP end of this example is shown in FIG. Comparing the sound of the speaker shown in =), which has less voltage change than the conventional speaker shown in RL,
Compared to conventional models, the noise generated when starting up the amplifier has become smaller. Also, the startup time (T) of the amplifier has become faster.

<Effects of the Invention> According to the present invention, the area occupied around the power IC during product mounting is reduced. It also reduces the cost of the product. Also,
Variations in IC characteristics due to feedback bin capacitance are eliminated.

Also, startup time is faster.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing one embodiment of the present invention, and FIG.
The figure is a waveform diagram comparing a conventional example and an example. Patent application Representative of Toppan Printing Co., Ltd. Kazuo Suzuki (a) (c) [Ron (=) Figure 2

Claims (1)

[Claims] An amplifier power supply circuit consisting of a fluctuation compensation circuit that feeds back fluctuations from the voltage type amplifier circuit in reverse phase to the constant voltage circuit used in the front stage of the power amplifier.