JPH03155365A - Power supply - Google Patents

Abstract

PURPOSE:To prevent overcurrent at the time of start-up by providing a circuit, for detecting the output current and correcting the fluctuation at the time of start-up, for each of a plurality of switching regulators to be operated in parallel. CONSTITUTION:Output current from a stabilizing control circuit 13 for switching regulators 11A, 11B, to which a plurality (two in the Figure) of outputs are connected in parallel, is detected 22 thus producing a correcting output voltage 24 proportional to the output current. When the correcting voltage 24 is lower than an output voltage 17 at a branch point, obtained by dividing a reference voltage 16 by means of resistors R1, R2 a current correcting circuit 23 functions. The branch point output voltage 17 rises with a time constant determined by the resistors R1, R2, R3 and the output impedance of a diode D and the current detecting circuit 22. When the output current rises to a prescribed range, the diode D is reversely biased to stop function of the current correcting circuit 23 thus fixing the branch point output voltage 17. By such arrangement, irregularity of start-up time is suppressed resulting in prevention of overcurrent at the time of start-up.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention connects the output terminals of a plurality of switching regulators that convert input terminals into stabilized direct current, and converts the stabilized direct current into a load. related to power supply circuits that supply power to

[Conventional technology]

Conventionally, as this type of power supply circuit, there is one shown in FIG. 3, for example. This power supply circuit connects the output terminals of two switching regulators IIA and IIB, and supplies stabilized direct current to a load 12 by operating these two switching regulators IIA and IIB in parallel.

Since the switching regulators IIA and IIB have the same configuration, the A-system switching regulator IIA will be explained. The switching regulator IIA includes a stabilization control circuit 13 that makes the input terminal a predetermined stabilized direct current;
A slow start circuit 14 built into the stabilization control circuit 13 for smoothly starting power supply to the load 12
and a voltage dividing circuit 15.

The voltage dividing circuit 15 divides the base ds voltage 16 contained in the stabilization control circuit 13 using voltage dividing resistors R+ and R2.
The voltage division point output voltage 17 is input as a control voltage 18 to the slow start circuit 14 and the internal control section. By changing this voltage division point output voltage 17, the operation of the switching regulator 11A is controlled. That is, when the switching regulator 11 is off, the transistor 19 in the slow start circuit 14 is on, and both terminals of the capacitor 20 are short-circuited.

Therefore, since the branch point output voltage 17 is maintained at the reference voltage 16, the control voltage 18 to the internal control section exceeds the control range, and the switching regulator IIA does not operate. On the other hand, in order to operate switching regulator IIA, transistor 19 is turned off. Then,
The capacitor 20 is charged, and the voltage dividing point output voltage 17 of the voltage dividing circuit 15 begins to gradually decrease toward the value determined by the voltage dividing circuit 15, as shown in FIG. 4(a). When the voltage division point output voltage 17 enters the control range of the internal control section at time t1, the conduction period of the switching element within the internal control section gradually expands from zero and begins operation. And Figure 4 (
As shown in b), when the output voltage 21 of the switching regulator 11A reaches a predetermined value at time t2,
The energization period is almost constant.

[Problem to be solved by the invention]

However, such switching regulator IIA
,],],B in parallel operation, the output terminals of the two switching regulators 11A and IIB are connected in parallel, so that the individual switching regulators 11Δ
, IIB and variations in the slow start time cause variations in the rise of the output current.

For example, the output current of switching regulator IIA in system A rises quickly as shown in Figure 4 (C), and the output current of switching regulator IIB in system B rises quickly as shown in Figure 4 (d).
), the faster system A has already reached its maximum supply capacity, while the slower system B remains close to zero amps.

In this way, in conventional slow start circuits, in the case of parallel operation, no correction is made to the magnitude of the output current rise when the power supply starts up, so if the output current rises quickly, it will reach the drooping point. Otherwise, the overcurrent detection point is reached and the rise time of the output voltage becomes extremely long, or the overcurrent is detected and the output voltage shuts down.

[Failure to solve the problem]

The present invention includes a current detection circuit that detects the value of the output current in each switching regulator and outputs it as a correction voltage, and a current correction circuit that corrects variations in the output current based on the correction voltage. It is characterized by having the following.

[Effect]

As a result, the output current of a plurality of connected switching regulators is made to rise quickly if the output current rises slowly, and if the output current rises quickly, the output current does not rise quickly when the output current reaches a specified value.

〔Example〕

Next, one embodiment of the present invention will be described with reference to FIGS. 1 and 2.

FIG. 1 is a block diagram of a power supply circuit according to the present invention, and the same components as those in the conventional example shown in FIG.

In the present invention, a current detection circuit 22 that detects the value of the output current and a current correction circuit 23 that corrects variations in the rise of the output current are additionally provided in addition to the conventional circuit.

The current detection circuit 22 detects the value of the output current and outputs a correction voltage 24 proportional to the detected output current value, and when this correction voltage 24 is smaller than the branch point output voltage 17, current correction is performed. Circuit 23 operates. That is,
Since the output current value is zero or a small value when the output voltage rises, the correction voltage 24 of the current detection circuit 22 is also zero or a small value, and is smaller than the branch point output voltage 17.

Therefore, the current correction circuit 23 operates. In other words, the branch point output voltage 17 of the voltage dividing circuit 15 is connected to the capacitor 20 and the resistor R.
+, the time constant determined only by R4, but the resistor R3 of the current correction circuit 23, the diode D, and the current detection circuit 22
It will fall with a time constant that also includes the output impedance of. Then, when the output current rises to within the specified range, the diode D is reverse biased and the current correction circuit 23
stops working. As a result, the branch point output voltage 17
is fixed at a potential determined by resistors R1 and R2.

As a result, switching regulator 11A111B
If there is variation in the rise of the output current between the two, the operation of the current correction circuit 23 is such that the diode D is reverse-biased earlier in the case where the output current rises faster, and correction is made so that the rise of the output current becomes slower.

FIG. 2 is a characteristic diagram showing its operation. Now, assuming that the output current of the A-system switching regulator 11A rises quickly and the output current of the B-system switching regulator IIB rises slowly, the operation of the current correction circuit 23 causes the output current to rise as shown in FIG. 2(a). , the branch point output voltage 17a of the switching regulator IIA falls slower than the output voltage 17b of the switching regulator IIB.As shown in FIG. Branch point output voltage 17a,
17b starts rising at the time t when it enters the control range. FIG. 2(C) shows the output current of the A system, and FIG. 2(d) shows the output current of the B system.

〔Effect of the invention〕

As explained above, the present invention prevents the detection of overcurrent at the time of start-up by correcting so that the variation in the value of the rise of the output current at the time of start-up is reduced between a plurality of switching regulators that operate in parallel. be able to. In addition, in parallel operation of the drooping method, there is an effect of preventing the voltage rise time from becoming abnormally long due to entering the drooping point at the time of rise.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an embodiment of the present invention, Fig. 2 is a characteristic diagram showing the operation of the present invention, Fig. 3 is a block diagram showing a conventional example, and Fig. 4 is a characteristic diagram showing the operation of the conventional example. It is a diagram. 11...Switching regulator, 12...
...Load, 13...Stabilization control circuit, 14
...Slow start circuit, 15...Voltage divider circuit, 16...Reference voltage, 17...
Branch point output voltage, 18... Control voltage, 19...
...Transistor, 20...Capacitor,
21... Output voltage, 22... Current detection circuit, 23... Current correction circuit, 24...
・Correction voltage. Applicant NEC Corporation Ibaraki NEC Co., Ltd. Agent Patent attorney Umeo Yamauchi No. 3 Figure 11Δ

Claims (1)

[Claims] a stabilization control circuit that converts an input voltage into a stabilized direct current; a voltage divider circuit that divides a reference voltage; a slow start circuit that gradually increases the output voltage; a current detection circuit provided in the stabilization control circuit that detects the value of the output current and outputs it as a correction voltage;
and a current correction circuit that corrects the branch point output voltage according to the magnitude of the correction voltage so that the output current rises faster when the branch point output voltage is larger than the correction voltage. A power supply circuit characterized in that the output terminals of a plurality of switching regulators are connected to each other for parallel operation.