JPS622856A - Switching regulator - Google Patents

Abstract

PURPOSE:To simplify an insulating mechanism between input and output, and miniaturize the device while lightening the weight, by inserting a photo coupler into a circuit for the feedback of DC output voltage to a control circuit, and by driving the photo coupler with the power source of the control circuit. CONSTITUTION:A main switching circuit 10 is controlled by a control circuit 8 via a transformer 9, and so far as a switching regulator for conducting the output to a rectification circuit 12 and a smoothing circuit 13 via a main transformer 11 is concerned, DC output voltage is detected via a photo coupler 18 for feedback to the control circuit 8. The photo coupler 18 is driven by an auxiliary power source 16 for feeding current to the control circuit 8. As the result, a feedback loop is electrically insulated on the way, and a transformer or the like for insulation between input and output is not required to be set in the auxiliary power source 16.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention relates to reducing the size and weight of a switching regulator.

[Conventional technology]

FIG. 2 is a block diagram showing a conventional switching regulator when the input power source is AC. In the same figure, l, 2 are AC input terminals, 3 is an input filter,
4 is a rectifier circuit, 5 is an inrush current limiting circuit, and 6 is a smoothing circuit, and these constitute a power input circuit.

7 is an auxiliary power supply, 8 is a switching regulator control circuit (hereinafter referred to as a control circuit), 9 is a transformer, IO is a main switching circuit, 11 is a main transformer, 12 is a rectifier circuit,
13 is a smoothing circuit, and 14.15 is a DC output terminal.

AC input input from an input power source (not shown) to AC input terminals 1 and 2 passes through an input filter 3 and then a rectifier circuit 4.
The current is converted into a direct current, passed through an inrush current limiting circuit 5, and then shaped into a smooth direct current by a smoothing circuit 6. The input filter 3 functions to attenuate external noise and prevent internally generated switching noise from entering the power supply side. The rush current limiting circuit 5 functions to limit the rush current generated by the current flowing into a capacitor (not shown) of the smoothing circuit 6 when the power is turned on. DC voltage EI smoothed by smoothing circuit 6
N is supplied to the main switching circuit 10 and the auxiliary power supply 7. The auxiliary power supply 7 adjusts the input DC voltage with a sub-switching circuit 7a, rectifies and smoothes it with a rectifier and smoothing circuit 7c input via a transformer 7b, and outputs the rectified and smoothed voltage, thereby driving the control circuit 8. It becomes a DC power supply for

The control circuit 8 includes a drive circuit 8a, a PWM converter circuit,
It consists of an error amplification circuit 8C. The error amplification circuit 8c receives the DC output voltage EO sent out through the DC output terminal 14.15.
[lT is input as a feedback, and this is used as the reference voltage Es
, the error is amplified and the PWM converter circuit 8b
Enter. The PWM converter circuit 8b provides a pulse signal whose pulse width is modulated according to the output voltage of the error amplifier circuit 8c to the drive circuit 8a. The drive circuit 8a divides the pulse signal into the number of arm phases of the main switching circuit 10, and supplies it to the main switching circuit 10 via the transformer 9 as an on/off control signal. The main switching circuit 10 is driven on and off to switch the DC voltage EIN supplied from the smoothing circuit 6 so that the error amount becomes zero. The output of the main switching circuit IO is supplied to the rectifier circuit 12 via the main transformer 11, where it is converted into a DC voltage, and then waveform-shaped by the smoothing circuit 13.
4.15.

[Problem that the invention seeks to solve]

In this conventional circuit, the input power supply side and the DC output side are insulated by the main transformer 11 of the main circuit, the transformer 9 of the control circuit 8, and the transformer 7b of the auxiliary power supply 7. However, there were problems in that the process became complicated, the overall size of the device increased, the weight increased, and the price increased.

This invention was made to solve the above-mentioned conventional problems.By using a photocoupler to insulate the input power supply side and the DC output side, the configuration of the auxiliary power supply is simplified, and the device is made smaller and lighter. The purpose of the present invention is to obtain a switching regulator that can realize increased efficiency and cost reduction.

[Means to solve the problem]

In order to achieve the above object, the present invention has a configuration in which a photocoupler is inserted into a circuit that feeds and breaks a DC output voltage to a control circuit, and the photocoupler is driven by an auxiliary power source that is a power source for the control circuit.

[Effect]

In this invention, the auxiliary power supply is isolated from the DC output circuit side by a photocoupler, so the auxiliary power supply does not require a transformer to insulate between input and output as in the past, and voltage adjustment is performed using a non-switching regulator. Therefore, the circuit configuration becomes simpler than the conventional one.

〔Example〕

FIG. 1 is a block diagram showing one embodiment of the present invention.

In the figure, 16 is an auxiliary power supply, which is composed of a non-switching type regulator (series regulator) 16a and a smoothing circuit 16b, into which the DC voltage smoothed by the smoothing circuit 6 is introduced, and the voltage is adjusted to a predetermined level by the regulator 16a. DC voltage is supplied to the control circuit 8. 18 is a photocoupler, and the photodiode 18a is a resistor 1.
The collector of the phototransistor 18b is connected to the positive terminal of the auxiliary power supply 16, and the emitter is grounded via a resistor 19. The voltage is input to the error amplification circuit 8c of the control circuit 8 as a feedback signal.

Since the other configurations are the same as those in FIG. 2, the same reference numerals are given and explanations will be omitted.

Next, the operation of this device will be explained.

As in the conventional case, the main switching circuit 10 operates under pulse width control by the control circuit 8 to switch the DC input so that the DC output voltage E 011T becomes the reference voltage Es. From this state, the DC output voltage E 01lT
When the voltage becomes higher than the reference voltage Es, the current flowing through the photodiode 18a of the photocoupler 18 increases correspondingly, and the amount of light emission increases. As a result, the phototransistor 18b
The voltage drop across the resistor 19 increases, and the input voltage of the error amplifier circuit 8C increases. PWM
The output of the converter circuit 8b becomes narrower during its pulse in response to the increment of the input of the error amplifier circuit 8C, and the average output of the main switching circuit 10 decreases, causing the DC output voltage E OU
T is adjusted to a reference voltage Es.

In this embodiment, since the auxiliary power supply 16 is insulated from the DC output side by the photocoupler 1-8, there is no need to insulate it from the input side of the main switching circuit 10, and therefore a conventional transformer is not required. 7b is unnecessary, and a non-switching type regulator 16a may be used in place of the sub-switching circuit 7a, making the circuit configuration simpler, smaller, and lighter than the conventional circuit.

Note that the input power source of the present invention is not limited to an AC power source, and the control circuit 8 is not limited to that of the above embodiment.

〔Effect of the invention〕

As explained above, this invention uses a photocoupler to isolate the power input circuit and the DC output circuit, so there is no need to isolate the auxiliary power supply from the power input circuit, so the auxiliary power supply can be configured easily. This makes it possible to make the device smaller, lighter, and lower in cost than before.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a block diagram showing the circuit configuration of a conventional switching regulator. In the figure, 6-- Smoothing circuit, 8- Control circuit, 9- Transformer, 10- Main switching circuit, 11- Main transformer, 12- Rectifier circuit, 13- Smoothing circuit, 14.15
--- DC output terminal, 16--auxiliary power supply, 17.19--resistor, 18--photocoupler. In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] A main switching circuit, a control circuit in which a control signal that feedback-controls the switching operation of the main switching circuit and outputs it is coupled to the main switching circuit via a transformer, converts the output of the switching circuit input via the transformer into DC. A switching regulator is provided with a DC output circuit coupled to a DC output terminal, and an auxiliary power supply for driving the control circuit receives power from a power input circuit of the main switching circuit. A switching regulator characterized in that an output voltage is taken out between the DC output terminals via a photocoupler, and the photocoupler operates using the auxiliary power source as a driving power source.