JPH03155366A - Synchronous switching power supply - Google Patents

Abstract

PURPOSE:To prevent troubles due to beat frequency easily by interconnecting the synchronous terminals of a plurality of switching power supplies incorporating oscillator circuits thereby discharging a capacitor in the oscilator circuit quickly based on a synchronous signal. CONSTITUTION:Synchronous terminals 26 of a plurality (two in the Figure) of switching power supplies 21, 22 incorporating oscillator circuits 23 are interconnected. When an oscillator capacitor 1 is charged with a predetermined peak value through function of the oscillator circuit 23, a synchronizing signal is provided from a synchronizing signal generating circuit 27 and a switch 30 for a discharge circuit 28 is closed. Consequently, the capacitor 1 is discharged quickly through a counter flow preventing diode D29 and the switch 30, and the voltage across the capacitor 1 drops to a level equal to the sum of a reference voltage V and the voltage drop of D29. Upon elapse of a predetermined short time, the switch 30 is opened to resume charging operation. Consequently, the oscillator capacitors 1 in respective power supplies are discharged simultaneously and quickly thus preventing trouble due to beat frequency.

Description

[Detailed description of the invention] C Industrial application field J The present invention relates to an oscillation frequency synchronized switching power supply.

[Prior Art] In the conventional switching device 11 of this type, a control IC for controlling a switching element is used in the M) operation circuit for stabilizing the DC output voltage, and this control IC has a built-in oscillation circuit. Control pulses for the switching elements are formed based on the oscillation waveform.

Figure 7 shows the circuit components of a symmetric triangular wave oscillator, which is an example of an oscillation circuit built into a control IC. 3 is a switching means, 4 is a constant current circuit for discharging, and 5 is a voltage detection circuit for determining the peak value voltage and valley voltage of the oscillation waveform. Then, a constant current is supplied to the oscillating capacitor 1 via the charging constant current circuit 2 to charge the oscillating capacitor 1, and the charging voltage of the oscillating capacitor 1 increases linearly. When this charging voltage reaches a specified peak value voltage, a signal is output from the voltage detection circuit 5, the switch means 3 is opened, and the charged charge of the oscillation capacitor 'v1 is discharged via the constant current circuit 4 for discharging, causing the oscillation. The voltage across capacitor 1 decreases linearly. When the voltage drops to a specified valley voltage, the switch means 3 is opened by a signal from the voltage detection circuit 5, and charging of the oscillation capacitor 1 is started. This operation forms an oscillation signal having a symmetrical triangular waveform as shown in FIG.

By the way, when multiple switching power supplies with different oscillation frequencies are operated independently or in parallel in the same R unit, it is known that a beat of the difference frequency is generated and has an adverse effect on peripheral equipment. Then, due to variations in the oscillation capacitor 1, constant current circuit 2.4, or voltage detection circuit 5, even if the oscillation circuit is designed with the same constant number, the oscillation frequency will vary, and this will cause a difference in frequency between multiple switching power supplies. There was a problem that occurred.

A common R-oscillation method and a master-slave method are known to solve this problem.

As shown in Fig. 9, the common oscillation method is built in multiple switching power supplies 6.7 and stops the operation of the lζ oscillation circuit.
One common light instead! The same oscillation signal is supplied from the device 8 to a plurality of power supplies 6.7, and a frequency difference between the power supplies 6.7 can be prevented. As shown in Fig. 10, the master-slave system connects the master terminal 10 of the master-only power supply 9 with a built-in oscillation circuit to the slave terminal 12 of the slave-only power supply 11 that does not have a built-in oscillation circuit. The power supplies 9 and 11 can be operated synchronously with the oscillation frequency of the master-only power supply 9.

[Problems to be Solved by the Invention] In the above-mentioned conventional technology, the common oscillation method requires a common oscillator to be provided outside the power supply, which increases the cost.
Even during standalone operation, an oscillator is required outside the power supply, which is inconvenient. Furthermore, it is inconvenient that two types of power supplies must be prepared, one for synchronous operation and one for individual operation. Furthermore, the master-slave system requires two types of power supplies, one for the master and one for the slave, which is inconvenient.

SUMMARY OF THE INVENTION An object of the present invention is to provide a synchronous switching power supply that can prevent the generation of a difference frequency by connecting the synchronous terminals of power supplies of the same type to each other.

[Means for Solving the Problems] The present invention provides a switching power supply having a built-in oscillation circuit with an oscillation frequency synchronization terminal for connecting a plurality of power supplies, and synchronizes by detecting a predetermined voltage of an oscillation waveform at this synchronization terminal. This is a synchronous switching power supply that is connected to a synchronous signal generating circuit that outputs a signal, and is provided with a discharging circuit that rapidly discharges the charging voltage of an oscillation capacitor in response to the synchronous signal.

[Function] In the present invention, by connecting the synchronous terminals of a plurality of M sources, the charging voltage of the oscillation capacitor of each power source is rapidly discharged at the same time.

[Example] Hereinafter, an example of the present invention will be described with reference to the accompanying drawings.

FIG. 1 shows a block diagram, and each of the plurality of switching power supplies 21 and 22 is provided with a control fc24 incorporating the oscillation circuit 23 shown in FIG. 7, for example. 25 is a load.

A synchronization terminal 26 is connected to the connection point between the control IC 24 and the external oscillation capacitor 1, and a synchronization signal generation circuit 27 and a discharge circuit 28 are connected to the synchronization terminal 26 located inside the power supply 21 and 22. is provided. During synchronous operation, multiple switching power supplies 111i21.22
By connecting the synchronous terminals 26 of the two units, synchronized operation is performed without causing a difference in frequency. When operating multiple units independently or asynchronously, by opening the synchronous terminals 26, the oscillation circuit 23 built in each power supply You can drive as is.

FIG. 2 is a circuit configuration diagram showing the synchronization signal generation circuit 27 and the discharge circuit 28, and the synchronization terminal 26 is connected to the connection point between the control IC 24 and the external oscillation capacitor 1 via a backflow prevention diode 29. The input terminal of the synchronizing signal generating circuit 27 is connected to the connection point between the oscillation capacitor 1 and the anode of the backflow prevention diode 29. Further, a series circuit of a switch means 30 and a reference voltage V is connected to the cathode side of the backflow prevention diode 29, and the switch means 30 is opened and opened by the output of the synchronization signal generation circuit 27, and the reverse flow is prevented. A discharge circuit 28 is formed by a prevention diode 29, a switch means 30, and a reference voltage V.
is formed. The synchronizing signal generating circuit 27 detects the voltage at one end of the oscillation capacitor, and when this detected voltage becomes less than a specified threshold voltage, the switching means 30 is activated for a certain short period of time.
This is the time to close.

Next, the operation will be explained with reference to the waveform diagram in FIG. The switch means 3 shown in FIG. 7 is opened and discharge is started. When the voltage of the oscillation capacitor 1 becomes lower than the specified threshold voltage at the falling edge of the oscillation waveform, a synchronization signal is output from the synchronization signal generating circuit 27 and the switch means 30 is opened. As a result, the charge in the oscillation capacitor 1 is rapidly discharged through the backflow prevention diode 29 and the switch means 30, and is reduced to the sum of the reference voltage V and the voltage drop VF of the diode 29.

Thereafter, after a certain short time T, the switch means 30 is opened and charging of the oscillation capacitor 1 is started. In this case, when the voltage of the oscillation capacitor 1 suddenly drops due to the rfl formation of the switch means 30, the switch means 3 of the oscillation circuit 23 is closed and a charging current is supplied, but the switch means 30 remains open for a certain period of time. Therefore, the charging current is
0 side and is not charged for a period of time T. in this case,
The voltage relationship at each part of the R vibration waveform is set as follows.

Peak value voltage〉Specified threshold voltage〉Valley voltage〉vvv
F Is Figure 4 as shown in Figure 1? This is a circuit configuration diagram when the synchronous terminals 26 of Ia switching power supplies 21 and 22 are connected to each other, and as shown in the figure, the discharge circuits 28 of each power supply 21 and 22 are connected to each other via the synchronous terminals Since they are connected, when one switch means 30 is opened, the charges in the oscillation capacitors 1 of each power supply 21 and 22 are simultaneously rapidly discharged through the respective backflow prevention diodes 29 through the other switch means 30 which is opened. This results in
The oscillation period T^ of the power supply 21 shown in FIG. 5(a) and the oscillation period T^ of the power supply 21 shown in FIG.
Even if there is a deviation in TO between the oscillation period TB of the power source 22 shown in b), the waveform initially generated by the switch means 30, that is, the oscillation waveform VA of the power source 21 shown in FIG. 5(a)
At the same time as the rapid discharge when the switch means 30 is opened, the oscillation waveform Vs also rapidly discharges in a strong serial manner, and as a result, the oscillation waveform VB of the power supply 22 becomes a waveform synchronized with the oscillation waveform V^ as shown in FIG. 5(C). VB', thus eliminating the difference frequency between the multiple power supplies 21,22.

FIG. 6 is a circuit configuration diagram showing an example of the synchronization signal generation circuit 27, which shows the voltage of the oscillation capacitor 1 and the set voltage +
A comparator 31 is provided to compare the voltage yrer and an OR time constant circuit consisting of a resistor 32 and a capacitor 33 provided on the output side of the comparator 31, and an operational amplifier 34 to compare the charging voltage of the capacitor 33 and the set voltage +V ref. A timer circuit 35 consisting of
6 bases are connected.

The timer circuit 35 sets IIT when the switch means 30 is turned on, and prevents variations in the rise start point of the oscillation waveform due to variations in the turn-on operation of the transistor 36.

In this operation, the voltage of oscillation capacitor 1 is set voltage + V r
When the output of the comparator 31 reaches a specified threshold voltage after being compared with ef, the output of the comparator 31 becomes high level and charging of the capacitor 33 starts based on the time constant. Turn on operation. By turning on the transistor 36, the charges in the oscillation capacitor 1 are rapidly discharged.

Thereafter, when the charging voltage of the capacitor 33 reaches a predetermined value after a time T, the output of the operational amplifier 34 becomes low level, the transistor 36 is turned off, and charging of the oscillation capacitor 1 starts.

As described above, in the embodiment of the present invention, it is possible to perform synchronized operation that prevents the generation of a difference frequency, as shown in the oscillation waveform of Fig. 5, by simply connecting the synchronization terminals of multiple units of the same ladder power supply. In addition, when operating a plurality of units independently or asynchronously, by opening the synchronous terminals, the oscillation circuits built into each power supply can be used to operate with the oscillation waveform shown in FIG. 3.

This solves problems such as the conventional common oscillation system, which requires an external common oscillator, which increases cost, and the master-slave system, which requires two types of power supplies, one dedicated to the master and one dedicated to the slave, which is inconvenient.

Note that the present invention is not limited to the above-mentioned embodiments, and various modifications can be made within the scope of the gist of the present invention. For example, the oscillation circuit shown in Fig. 4 and the synchronization signal generation circuit shown in Fig. 6 are merely examples, and may be selected as appropriate (＼. Also, the waveform of the oscillator is not limited to a symmetrical triangular wave. It can be applied to various things.

[Effects of the Invention] The present invention rapidly discharges the charging voltage of the oscillation capacitor of each N source by connecting the synchronous terminals of multiple power supplies, and therefore generates a difference frequency easily and economically. Qin has the effect of being able to prevent.

[Brief explanation of the drawing]

1 to 6 show one embodiment of the present invention, FIG. 1 is a schematic explanatory diagram showing a synchronous operation state, FIG. 2 is a circuit configuration diagram,
Fig. 3 is an oscillation waveform diagram, Fig. 4 is a circuit diagram showing a synchronous operation state, Fig. 5 is an oscillation waveform diagram, Fig. 6 is a circuit diagram showing a synchronous signal generation circuit, and Fig. 7 is a general circuit diagram. A circuit configuration diagram showing an oscillation circuit, Fig. 8 is a general oscillation waveform diagram, Figs. 9 and 10 show conventional examples, Fig. 9 is a schematic explanatory diagram of a common oscillation method, and Fig. 10 is a master-slave diagram. FIG. 2 is a schematic explanatory diagram of the method. 21, 22...Switching power supply 23...Oscillation circuit 26...Synchronization terminal 21...Synchronization signal generation circuit 28...bIi electric circuit patent Applicant: Nemic-Lambda Co., Ltd. Agent: Patent attorney Mamoru Ushiki

Claims (1)

[Claims] A switching power supply having a built-in oscillation circuit is provided with an oscillation frequency period terminal for connecting a plurality of power supplies,
A synchronization signal generation circuit that detects a predetermined voltage of the oscillation waveform and outputs a periodic signal is connected to the synchronization terminal, and a discharge circuit that rapidly discharges the charged voltage of the oscillation capacitor by the synchronization signal is provided. Synchronous switching power supply.