JPS60200765A - Multioutput switching regulator - Google Patents

Abstract

PURPOSE:To obtain a stable operation by synchronizing two switching regulators in a circuit for producing two different output voltages by connecting switching regulators in two stages, thereby preventing a noise or a beat from generating. CONSTITUTION:In a circuit for producing two different output voltages V1, V2 by connecting the first switching regulator 11 with the rear stage of an AC rectifying and smoothing circuit 13, and connecting the second switching regulator 12 through a transformer 16, a differentiator 17 is connected with the output side of the transformer 16, and the output is used as a trigger signal of the second switching regulator (self-oscillation type) to synchronize the oscillating frequency of the regulator 12 which the oscillating frequency of the regulator 11.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to improvements in multi-output switching regulators.

(b) As a conventional multi-output switching regulator, JP-A-56-
As shown in Japanese Patent No. 127217, it is known to obtain multiple outputs of different voltages from multiple secondary windings of a transformer.However, in this method, the output voltages of multiple outputs are set by the design of the transformer. There was a drawback that the output voltage could not be obtained arbitrarily.

Therefore, as shown in the first section, it is composed of a first switching regulator and a second switching regulator (5),
The output voltage of the first switching regulator is used to obtain a different output from the second switching regulator. The first switching regulator uses an offline type, and its configuration is to convert commercial AC power into DC using a rectifier and smoothing circuit (]), and a control circuit (2
) The switching transistor (3) is switched by a high frequency pulse of, for example, 20 to 50 KHz, and a voltage stabilized by the ferrite φ transformer (4), which is the collector load of the switching transistor (3), is obtained from the secondary side. . The control circuit (2) is composed of a pulse oscillator, a pulse width modulation circuit, and a drive circuit, and is normally used at a low voltage of about 5 to 10V.

The second switching regulator (5) is called a DC-DC converter, and is composed of a self-oscillation type chopper circuit that obtains an output V2 different from the secondary output V1 of the first switching regulator. This chopper type constant voltage power supply circuit is shown in FIG.

Tr4 is a switching transistor and performs switching of the DC power source v1. Diode D1 coil L
, capacitor C2 and switching transistor Tr are rectified and smoothed to obtain a stabilized output voltage (2).

Tr and Tr2 constitute a differential circuit, and constitute an error amplifier that detects an error between the reference voltage caused by the Zener diode ZD and the output voltage (2). Tr3 drives the switching transistor Tr4, and is controlled by the output of the error amplifier. Further, C2 forms a positive feedback loop and constitutes a self-excited oscillator.

In the above multi-output switching regulator, the oscillation frequency of the first switching regulator operates independently and independently of the oscillation frequency of the second switching regulator. For this reason, the same power supply circuit has multiple oscillation frequencies for switching, which increases the noise level, and because the oscillation frequencies are different, the noise frequency band becomes wide and the means for noise suppression becomes complicated. There were drawbacks that made it difficult. Furthermore, when the two oscillation frequencies are close to each other, they interfere with each other, causing a kind of disordered state called a beat, which makes the circuit system unstable and, in particular, increases the noise level.

(c) Purpose of the Invention The present invention has been made in view of the above drawbacks, and provides a multi-output switching regulator in which the oscillation frequency of the second switching regulator is synchronized with the oscillation frequency of the first switching regulator, thereby eliminating the disadvantages of the conventional switching regulator. Our goal is to provide the following.

B) Structure of the Invention The multi-output switching regulator according to the present invention applies an AC voltage generated by switching a switching element at a predetermined oscillation frequency to the primary winding of the transformer, and applies the AC voltage generated by switching the switching element at a predetermined oscillation frequency to the primary winding of the transformer. In a multi-output switching regulator comprising a first switching regulator that obtains an output voltage and a self-oscillation type second switching regulator that uses the first output voltage as an input voltage to obtain a different second output voltage. , the oscillation frequency of the second switching regulator is synchronized with the oscillation frequency of the first switching regulator.

(E) Embodiment An embodiment of the present invention will be described with reference to FIGS. 3 and 4. The multi-output switching regulator according to the invention has a first switching regulator αυ and a second switching regulator a2.

The first switching regulator αυ uses an off-line type similar to the conventional example shown in FIG. A voltage stabilized by switching the switching transistor (151 and ferrite transformer α6 which is the collector load of the switching transistor u4) with a 50KHz pulse is obtained from the secondary side.

The control circuit α is composed of a pulse oscillator, a pulse width modulation circuit, and a drive circuit. The second switching regulator 02) is also called a DC-DC converter, is composed of a self-excited oscillation type chopper circuit, and forms a DC output ■2 different from the DC secondary output ■1 of the first switching regulator αυ.

The feature of the present invention is that in such a configuration, the oscillation frequency of the second switching regulator (one oscillation frequency is synchronized with that of the first switching regulator 01). That is, as is clear from FIG. 3, a trigger signal is formed from the AC secondary output of the first switching regulator I using the differential circuit α of the CR, and this trigger signal is applied to the second switching regulator IJZJVC to determine the oscillation frequency. It is synchronized.

A more specific circuit is shown in FIG. The second switching regulator θ2 includes a switching circuit section (I output rectifier section (19), an error amplifier section (201), a control circuit section (
2υ and synchronous trigger circuit section (consisting of 2 υ).

Switching circuit section U Dark switching transistor T
r3 and the resistor R0 connected between its base and emitter
Consists of. The switching circuit section 0110 operates to switch the DC power input and modulate the ON/OFF ratio to obtain a predetermined output voltage.

Output rectifier (l→ is diode D2, inductance L
and a capacitor C1, the output of the switching circuit section 0 is rectified by a diode D, and smoothed by a smoothing circuit composed of an inductance L and a capacitor C2, resulting in a stable output voltage. I am getting .

Error amplifier 1 (2o+ is resistor R1, R3, and R5,
A reference voltage is applied to the base of the transistor Tr, and an output voltage V is applied to its emitter. is being applied. Here, the reference voltage is obtained by connecting a resistor R6 and a Zener diode ZD in series to the DC power supply input, and dividing the Zener voltage of the Zener diode ZD by a resistor R3ΦR4. Thereby, a reference voltage lower than the Zener voltage of the Zener diode ZD can be realized.

Control circuit section a provides resistors R2 and R7, transistor Tr2
and a capacitor C1, and a transistor Tr2
The output of the error amplifier section Qo) is applied to the base of
The emitter of the transistor Tr2 is connected to the base of the transistor Tr3, the collector of the transistor Tr2 is positively fed back to the base of the transistor Tr1 via the capacitor C1, and the control circuit section 04I works together with the error amplifier section (2o). It performs self-oscillation.

Synchronous trigger circuit section (22 is resistor R8 and capacitor C8
The secondary AC output of the transformer Oe is differentiated to form a differentiated waveform, and this differentiated waveform is used as a trigger signal to be sent to the error amplifier section via the diode D3 for backflow prevention. A voltage K is applied to the base (point D) of the transistor Tr.

Next, the operation of the second switching regulator (Iz) will be explained with reference to FIG. 5. The waveforms shown in FIG. When the differential waveform shown in FIG. 5E is applied to the base of the transistor Tr through the diode D, the transistor Tr1 becomes conductive. becomes conductive, and the switching transistor Tr3 of the switching circuit section U→ also becomes conductive.Furthermore, the voltage at the collector of the transistor Try also rises as shown in FIG.
is positively fed back to the base of the transistor Trl to maintain conduction of the transistor Trl. On the other hand, when the output voltage v2 rises due to conduction of the transistor Tr3, the emitter potential of the transistor Tr1 rises and the transistor Trl is cut off.

Along with this, the transistor Tr2 is also cut off, the transistor Trs is also cut off, and the charge in the capacitor C1 is also discharged.

This ON/OFF cycle is repeated.

The conditions necessary to stably synchronize the second switching regulator α with the pasted configuration of the present invention are as follows: First, in order to reliably trigger the transistor Tr, the trigger voltage Va must be set to V, ≧ Set to VI10VII-(VI+0.6)V.

Second, in order to achieve stable operation, the oscillation frequency f of the second switching regulator (12ρ in the self-excited state) is larger than the oscillation frequency f1 of the first switching regulator αυ.

The goal is to maintain a relationship of mutual respect.

Note that since the second switching regulator 02) has a positive feedback loop, it is sufficient even if the energy as a trigger is small.

(f) Effects of the Invention According to the present invention, the second switching regulator (12
Since + can be operated synchronously, it is possible to suppress the generation of noise and prevent the generation of beats. Furthermore, multiple switching regulators can be operated stably, and any output voltage can be easily achieved. Furthermore, by selecting the constants of the differentiating circuit, it can also operate as a spike absorbing circuit, and spike noise to the output can be reduced.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram explaining a conventional multi-output switching regulator, FIG. 2 is a circuit diagram explaining a conventional self-oscillation type chopper circuit, and FIG. 3 is a circuit diagram explaining a multi-output switching regulator of the present invention. 4 are circuit diagrams for explaining the second switching regulator of the present invention, and FIG. 5 is a waveform diagram for explaining the operation of the second switching regulator of the present invention. Explanation of main drawing numbers uI) is the first switching regulator, u21 is the second switching regulator, (16) is the transformer, 0 dark switching circuit section, α group is the output rectification section, 4 is the error amplifier section, ■ υ is the control circuit section, (2 is the synchronous trigger circuit section. Applicant: Sanyo Electric Co., Ltd. and one other person.

Claims (1)

[Claims] (1) A first switching regulator that applies a current voltage generated by switching a switching element at a predetermined oscillation frequency to the primary winding of the transformer to obtain a first output voltage from the secondary winding of the transformer; and a self-oscillation type second switching regulator that obtains a different second output voltage using the first output voltage as an input voltage, wherein the oscillation frequency of the second switching regulator is A multi-output switching regulator whose tightening mechanism is to synchronize the oscillation frequency of the first switching regulator with the oscillation frequency of the first switching regulator.