JPH0389851A - Resonance type switching power source - Google Patents

Abstract

PURPOSE:To maintain resonance conditions and to enhance an efficiency and stabilization by providing secondary side switching means and control means for controlling it ON/OFF between the secondary winding of transforming means and smoothing means. CONSTITUTION:In a resonance type switching power source having a switching element Qm for switching a primary voltage Vin, a capacitor Cm resonated with the inductance of a transformer T, switching elements Q1,..., Qn for respectively controlling secondary side output voltages V01,..., V0n, and control means for outputting switching commands B, D in comparison of secondary side outputs A, C with a target stabilization voltage are provided. The control means turns ON the commands B, D when the outputs A, C are lower than a target stabilization voltage and turns them OFF in the case of vice verse. Thus, an output voltage can be effectively obtained stably for large variations in an input voltage and a load.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to a resonant switching power supply used as a power supply for office automation (OA) equipment and the like.

(Prior art) The idea is to reduce the overlap between voltage and current during turn-on and turn-off by coupling a resonant circuit in parallel to a switching element that intermittents the input voltage and changing the current or voltage in a sinusoidal manner. A switching power supply using this method is called a resonant switching power supply.

Since such a resonant switching power supply does not involve steep voltage changes or current changes, it has characteristics of not only low loss but also low noise.

Figure 5 shows such a resonant switching power supply, where the symbol Vln is the input voltage from a battery or a DC input power source whose AC input has been rectified and smoothed, and the symbol Q11 is the input voltage from a power transistor, power Mo5-PET, etc. The switching element 1 is a frequency modulator (FM) that controls the on-pulse width of the switching element Q by the change in resonance frequency or the change in the input terminal Vin and the magnitude of the current of the diode Da, which will be described later. driver CD that controls the on-pulse width of the switching element Qs)
are shown respectively.

Further, in the same figure, the symbol T is a transformer having a primary winding Ta and secondary windings Tb1-Tbn, and the secondary winding side has multiple outputs, and the symbol CI is a resonance that resonates with the inductance L of the primary winding Ta. The capacitor, number 1 is a diode that regenerates the energy of the transformer T to the input power supply, symbol R is a resistor that informs the frequency modulator 1 of the magnitude of the load current, and symbol DI-Dn is a diode that transmits the current to the load side during flyback. The rectifying diodes, symbols C1 to Cn, are smoothing capacitors, symbols vO1 to VOn, which smooth the output voltage to the load.
indicates the output voltage from each output terminal.

In such a resonant switching power supply, a resonant capacitor Cm connected in parallel to the switching element Qm
By using the diode DI and the switching element Qw, the switching loss during turn-on and turn-off of the switching element Qw can be reduced to zero, and furthermore, the noise generated by the switching element Q- can be reduced.

In addition, in such a resonant switching power supply, the on-pulse width of the switching element Qs can be controlled by feeding back the output a of the output voltage VOI to the frequency modulator 1, so that each output voltage VO1=VO
n is stabilized.

However, in such a resonant switching power supply, when the load current of the output voltage VOI changes significantly, there is a limit to keeping the output of each output voltage VOI to VOn constant with high accuracy. In such a case, the limit can be alleviated by incorporating dropper circuits Drl to Drn on the secondary side, but the dropper circuit Drl=D
Since rn is expensive, the cost increases, and the power consumption in the dropper circuit Drl-Drn increases, resulting in a decrease in efficiency.

Furthermore, there is a limit to maintaining resonance conditions due to fluctuations in input voltage Vin and load.

(Problem to be Solved by the Invention) As described above, in the conventional resonant switching power supply described above, there is a limit in stabilizing each output voltage when the load current of the output voltage changes greatly. In such cases, this limitation can be alleviated by incorporating a dropper circuit on the secondary side, but the cost increases because the dropper circuit is expensive, and the efficiency decreases due to increased power consumption in the dropper circuit. may decrease.

There was also a limit to maintaining resonance conditions due to fluctuations in input terminals and loads.

The present invention was made in response to these circumstances, and
It is an object of the present invention to provide a resonant switching power supply that can maintain resonance conditions, achieve high efficiency at high frequencies, and achieve highly stable output.

[Structure of the Invention] (Means for Solving the Problems) In order to remotely achieve the above object, the resonant switching power supply of the present invention includes a primary side switching means that connects and disconnects the input terminal, and a resonant switching power supply that connects the input terminal in parallel with the primary side switching means. a resonant circuit that is connected to the primary side switching means and keeps the voltage between the terminals at zero when the primary side switching means is turned on and off; a transformer means that transforms the voltage interrupted by the primary side switching means; and a voltage transformed by the transformer means. a smoothing means for smoothing and outputting the voltage, a secondary side switching means provided between the smoothing means and the voltage transformation means and for intermittent voltage applied to the smoothing means, and an on/off control for the secondary side switching means. Based on the stabilization target voltage and the secondary side output, the operation is turned on when the secondary side output is smaller than the stabilization target voltage, and turned off when the secondary side output is larger than the stabilization target voltage. and control means for controlling.

(Function) In the resonant switching power supply of the present invention, the input terminals that are disconnected by the primary side switching means, whose voltage between the terminals is maintained at zero by the resonant circuit, are transformed by the transformer and smoothed by the smoothing means. output after

At this time, the control means controls the on/off operation of the secondary side switching means provided between the smoothing means and the voltage transformation means, based on the stabilization target voltage and the output of the secondary side. It is controlled so that it is turned on when the output on the secondary side is small and turned off when the output on the secondary side is larger than the stabilization target voltage.

Therefore, the number of resonant waveforms within a certain period of time can be varied, thereby controlling the apparent duty cycle of the resonant waveform occurring at the output side of the secondary side switching means. It can always output a stable voltage even when there are large fluctuations.

(Example) Hereinafter, details of an example of the present invention will be described based on the drawings.

FIG. 1 shows an embodiment of a resonant switching power supply according to the present invention. Note that parts common to those in FIG. 5 are given the same reference numerals, and redundant explanations will be omitted.

In the figure, the symbol VIn is the input voltage of the input power supply, the symbol QIl is the switching element, and the symbol 1 is the frequency modulator (P
M), code 2 is the driver (D), code T is the primary winding Ta
and a transformer having secondary windings Tb1-Tbn, symbol C- is a resonant capacitor, symbol Da is a diode, symbol R
is a resistance, code DI-Dn is a rectifier diode, code CI-
Cn represents a smoothing capacitor, and symbols V Ol-V On represent output voltages, respectively.

Further, in the figure, the symbol Ql=Qn indicates a secondary side switching element that thins out the voltage applied to the smoothing capacitor C1=Cn by an on/off operation.

FIG. 2 shows a control circuit that controls the on/off operations of the secondary side switching elements Ql-Qn.

In the same figure, E^1 to EAn are the stabilization target voltages V ``e
"Comparators that compare 1 and the output A of the secondary side, 3al~3
an is a control unit (
CONTI-CONTn), 4 al~4 a2
1 and 2 respectively indicate drivers (DI-Dn) that control the on-pulse widths of the secondary side switching elements Ql-Qn.

Next, the operation of the resonant switching power supply having such a configuration will be explained using FIG. 4.

First, information on changes in the input terminal Vin and changes in the load is input to the frequency modulator 1 manually.

Tsumari, input terminal VIN power AC case 11: AC90V
-AC260v, Louis is AC90V ~ACIIOV
Fluctuations between manometers, when input terminal Vin is DC 1. :
In order to satisfy the resonance condition due to fluctuations between 100V and 150V (7) and load fluctuations (fluctuations in the load current of the output voltage VOf-VOn), the resonant frequency -1/2πI" (However, L is the apparent value of the transformer T. induct dance,
C indicates the cavastance of the capacitor Cm) and determines the on-pulse width of the switching element QI.

Then, the input voltage Vln, which is interrupted by the switching element Q+g, is transmitted to each secondary winding mTb1-Tbn via the primary winding Ta of the transformer T, and then smoothed by the smoothing capacitor CI-Cn, and from the output terminal to the VOI ~V
It is output as an ON constant voltage.

At this time, the energy to the transformer T is large when the on-pulse width of the switching element Qm is large, and is small when the on-pulse width of the switching element Qm is small, depending on the resonance frequency, and the energy to the transformer T is small when the on-pulse width of the switching element Qm is small.
A voltage of V TOI to V Ton is output from bn.

That is, as shown in FIG. 4, each comparator EA of the control circuit
I~EAn is the stabilization target voltage Vre "n(1-1,2
,...) and the outputs A and C on the secondary side, when the output voltage VOn is smaller than the stabilization target voltage Vrel'n,
Each control unit 3a1 to 3an controls a secondary side switching element Q n (n= 1, 2+
), and conversely, when the output voltage VOn is larger than the stabilization target voltage V ref'n, the secondary side switching element Qn is instructed to be turned off.

The voltage comparison timing at this time is from 26 to 26 in the X part in the figure.
31, and for example at timing 26, the output voltage VOn is greater than the stabilization target voltage Vrefn, so the output D of the driver 4an is set to the off level.

As a result, the secondary side switching element Qn is turned off, so that the energy of 22-1 of the transformer output voltage VTOn is not supplied to the smoothing capacitor Cn, and the output voltage VOn decreases as shown in 2B to 27.

Furthermore, at timing 27, the stabilization target voltage V r
Since the voltage is lower than ern, the output D of the driver 4an becomes on level. As a result, the energy of 22-2 of the transformer output voltage V Ton is supplied to the smoothing capacitor Cn.

Similarly, the secondary side switching element Qn is instructed to turn on/off at each timing 28 to 31, and the timing voltage waveform 24 approaches the stabilized target voltage V rern, so that the stabilized output voltage VOI- VOn is obtained.

Here, when these controls are not performed, the output voltage VOn increases as shown by the voltage waveform 25 shown by the broken line, so
This means that stabilized output voltages VOI to VOn cannot be obtained.

FIG. 3 shows another embodiment in which the configuration of the control circuit shown in FIG. 2 is changed.

In the figure, reference numeral 5 is an A/D converter that converts the voltage of the output A-C on the secondary side into a digital value, and reference numeral 6 is an A/D converter that converts the voltage of the output A-C on the secondary side into a digital value. ~
Each figure shows a microcomputer control unit that controls the output of the 7an.

In the control circuit having such a configuration, when the A/D converter 5 converts the voltage of the output A-C on the secondary side into a digital value and sends this value to the microcomputer control section 6, the microcomputer control section 6 The magnitude with respect to the stabilization target voltage V rern shown in FIG. 4 is determined by calculation, and the output of each driver 7a1 to 7an is controlled in the same manner as described above, and the on/off operation of each secondary side switching cable Q1 to Qn is performed. control.

As described above, in this embodiment, the control circuit controls the on/off operation of the secondary side switching element based on the stabilization target voltage and the output of the secondary side, such that when the output voltage is smaller than the stabilization target voltage, the control circuit turns on/off the secondary side switching element. On the other hand, since it is turned off when the output voltage is higher than the stabilization target voltage, a stabilized output voltage can be reliably obtained even if there are large fluctuations in the input terminal or load.

In this example, a case has been described in which information on input voltage changes and load fluctuations is input into the frequency modulator in advance, but this is not limited to this example. A stable output voltage can also be obtained by operating with a constant on-width and performing on/off operations using a switching element on the secondary side.

[Effects of the Invention] As described above, according to the resonant switching power supply of the present invention, it is possible to maintain resonance conditions, increase efficiency at high frequencies, and achieve highly stable output.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the resonant switching power supply of the present invention, FIG. 2 is a block diagram showing a control circuit that controls the on/off operation of the secondary side switching element in FIG. 1, and FIG. The figure is a block diagram showing another embodiment in which the configuration of the control circuit shown in Fig. 2 is changed, Fig. 4 is a waveform diagram showing the operation of the resonant switching power supply shown in Fig. 1, and Fig. 5 is a conventional resonant switching power supply. FIG. 2 is a circuit diagram showing a type switching power supply. Vin...input voltage, Ql...switching element,
1... Frequency modulator (FM), 2... Driver (
D), T...transformer, Ta...-next winding Ta
, Tb1-Tbn...Secondary winding, C11...Resonant capacitor, Da...Diode, R...Resistor, D
I-Dn... Rectifier diode, C1-Cn... Smoothing capacitor, VO1-VOn... Output voltage, Ql-Q
n...Secondary side switching element, EAl-EAn-.
・Comparator, 3 at ~ 3 an...control unit (CON
TI~C0NTn), 4 at ~4 a2-...
Driver (DI-Dn) 5...A/D converter, 6...
・Microcomputer control unit.

Claims (1)

[Claims] (1) a primary side switching means for intermittent input voltage; a resonant circuit connected in parallel to this primary side switching means and keeping the voltage between the terminals at zero when the primary side switching means is turned on/off; and the above primary side. transformer means for transforming the voltage intermittent by the switching means; smoothing means for smoothing and outputting the voltage transformed by the transformer means; provided between the smoothing means and the transformer means, and for the smoothing means. A secondary side switching means that intermittents the applied voltage, and an on/off operation of this secondary side switching means, based on the stabilization target voltage and the output of the secondary side, 1. A resonant switching power supply, comprising: control means for controlling the power supply to be turned on when the output is small and turned off when the output on the secondary side is larger than the stabilized target voltage.