JP2646021B2 - converter - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a converter, and more particularly to a converter that is stable during parallel operation.

[Conventional technology]

2. Description of the Related Art Converters having a configuration in which a DC power supply is received, temporarily converted to AC, transformed into an AC voltage by a transformer, rectified, and then converted again to a desired DC output voltage are widely used. This converter includes a stabilized feedback loop configured to generate a pulse width modulation signal output by an off-the-shelf converter driving integrated circuit to drive the switching element and to detect and configure a DC output voltage. When the conversion frequency of the converter is increased, the capacitance of magnetic components such as a transformer and the capacitance of the capacitor is reduced almost in inverse proportion to the frequency. In recent years, the technology to increase the conversion frequency to about 500 kHz, reduce the capacitance used, eliminate all electrolytic capacitors that change with time, and extend the life of the converter and reduce its size Have been doing.

[Problems to be solved by the invention]

However, when this type of converter is operated alone, it operates stably, but when multiple units are operated in parallel, there is a unit where the operating frequency component of other units appears in the output and the inductor in the smoothing circuit is cut off. .
Due to these effects, the ripple of the DC output voltage changes discontinuously. As a well-known means, it is stable if only a phase compensation circuit consisting of a capacitor and a resistor is connected in parallel to the DC output voltage detection circuit. Operation may not be possible. This phase change at the time of cutoff is discontinuous, which has been a problem that the operation of the converter becomes unstable.

[Means for solving the problem]

In order to solve such a problem of the conventional device, the present invention includes an integrating circuit for integrating a pulse width modulation signal of a converter driving circuit in a stabilizing feedback loop of the converter, and a small triangular wave obtained by the integrating circuit. Is superimposed on the voltage stabilizing terminal of the converter drive circuit.

As the integration circuit, a resistor and a capacitor are connected in series between the voltage stabilizing terminal of the converter drive circuit and the common line, and a semiconductor switching element driven by pulse width modulation signal output is connected to both ends of the capacitor. It is also proposed to configure.

〔Example〕

FIG. 1 shows an embodiment of the present invention. Receiving the DC power supply E, the plus side is connected to the primary winding of the transformer T and the drain electrode of the switching element FET Q1 sequentially, and the minus side of the DC power supply E is connected to the source electrode of the FET Q1. At the same time, it becomes the common line on the primary side. Here, an on / off signal is supplied to the gate electrode of the FET Q1 from the output terminal a of the converter drive circuit U1 via the resistor R5. (The waveform is shown in FIG. 2). As the FET Q1 is turned on and off, an AC voltage is generated in the primary winding of the transformer T.

The converter drive circuit U1 is widely used as an off-the-shelf integrated circuit. The internal circuit includes a reference oscillation circuit for setting the switching cycle of the converter, a triangular wave generation circuit based on the reference oscillation circuit, a reference voltage source, an error amplifier for constant voltage, and an output level of the error amplifier. And a circuit for generating a pulse width modulation signal output based on the output of the comparator. FIG. 1 shows only the terminals directly necessary for the description of the present invention. That is, a pulse width modulation signal output terminal a, a reference voltage source terminal b, voltage stabilization terminals c and d, a negative feedback terminal e, and a capacitor and a resistor for determining the period of the reference oscillation circuit are connected. Terminals g and f to be grounded and a ground terminal h.

Then, the secondary winding of the transformer T is rectified and smoothed by the diode D1, the diode D2, the inductor L and the capacitor C3, and a desired DC output is obtained from the output terminals t1 and t2, and supplied to the load RL.

The DC output voltage is detected by a voltage divider including a resistor R6 and a resistor R7 and sent to the inverting terminal of the operational amplifier U2. Further, a reference voltage source Vref is connected to the non-inverting terminal of the operation measuring instrument U2. The output of the operational amplifier U2 is supplied to the light emitting section of the photocoupler PC via the resistor R5. This optical signal modulates the conductivity of the light receiving transistor of the photocoupler PC, and provides a stabilizing signal to the stabilizing terminal C of the converter drive circuit U1.

The output is supplied from the output terminal a of the converter drive circuit U1 to the base of the PNP transistor Q2 via the resistor R3. On the other hand, the light receiving transistor of the photocoupler PC, the resistor R2 and the capacitor C2 are supplied from the reference voltage generating terminal b of the converter drive circuit U1.
Are connected in series. The emitter and the collector of the PNP transistor Q2 are connected to both ends of the capacitor C2 via the resistor R4.

Here, a circuit including the capacitor C2, the resistor R4, the transistor Q2, and the resistor R3 constitutes an integrating circuit. These circuits do not exist and one end of resistor R2 is connected to capacitor C2
The conventional configuration is a state in which the common line is not directly connected to the common line. In the present invention, the capacitor C2 of the integration circuit is inserted into the resistor R2, and the voltage signal of the integration circuit is superimposed via the resistor R2.

Next, the operation will be described. The light receiving transistor of the photocoupler PC receives an error signal for stabilizing the output voltage, and its emitter is normally at a DC level of about 2V. This voltage is connected to the stabilizing terminal c of the converter drive circuit U1. The voltage signal of the capacitor C2 for generating the voltage of the integration circuit associated with the transistor Q2 is applied thereto via the resistor R2. Since the transistor Q2 is turned on / off by the transistor Q2 via the resistor R4 in the capacitor C2 of the integrating circuit, a small triangular wave starting from a substantially zero value is generated.

Accordingly, a minute triangular wave having a waveform shown in FIG. 2 (terminal c of U1), synchronized with the period of the converter and corresponding to the output of the pulse width modulation signal, is superimposed on the emitter of the light receiving transistor of the photocoupler PC. This minute triangular wave is a waveform obtained by integrating the output waveform of the converter drive circuit U1 and is substantially similar to the minute AC component waveform appearing at the output terminals t1 and t2. However, the influence of the operating frequency of other units and the output inductor A waveform which is not affected by the cutoff of L is obtained. This waveform is output from the output terminals t1 and t2 to the resistor R7.
Unlike the waveform detected by the capacitor C5 and the storage of the FET Q1, the delay of the inductor L of the output filter and the capacitor C3 is not included, so that the effect of compensating for the phase delay of the system, that is, the advance compensation is optimal. Therefore, by superimposing the waveform shown in FIG. 2 (terminal c of U1) on the stabilizing terminal c, it is possible to obtain advance compensation synchronized with its own operating frequency.

FIG. 3 is a diagram showing a relevant portion of an integrating circuit in another embodiment of the present invention. In the figure, converter drive circuit U1
Is divided by a resistor R13 and a resistor R14 from the output terminal a, and is connected to the base of the transistor Q5. The collector and the emitter of the transistor Q5 are connected to the base and the emitter of the transistor Q4, respectively. On the other hand, a constant potential is applied to the base of PNP transistor Q3 from reference voltage generation terminal b of converter drive circuit U1 via resistors R15 and R16.
The emitter / base of the PNP transistor Q3 is connected in parallel to the resistor R15 via the light receiving transistor of the photocoupler PC to which the optical signal has been transmitted in series. The PNP transistor Q3 receives the output voltage stabilizing signal, and its collector is connected to the stabilizing terminal c of the converter drive circuit U1. An integrating circuit consisting of a resistor R2, a capacitor C2, and a resistor R4 is connected to the collector, and the collector of the PNP transistor Q3 is a small triangular wave having the waveform shown in FIG. 2 (terminal c of U1) corresponding to the cycle of the converter. Superimposed. This circuit operates in the same manner as the circuit of FIG. 1, but has a faster response speed than the circuit of FIG. 1 because the phototransistor of the photocoupler PC operates in the constant voltage mode. And the saturation voltage when the discharge transistor of the capacitor C2 of the integrating circuit is turned on is the first.
It is lower than the circuit in the figure.

[Action and effect of the invention]

As described above, the present invention is characterized in that a minute triangular wave obtained by integrating the pulse width modulation signal of the converter driving circuit is superimposed on the voltage stabilizing terminal of the converter driving circuit. Thus, the phase of the stabilization loop of the converter can be corrected.

Therefore, not only when this converter is operated alone but also when a plurality of converters are operated in parallel, there is an effect that each converter operates stably in each operation mode without mutual interference.

[Brief description of the drawings]

FIG. 1 is a diagram showing an embodiment of a converter according to the present invention, FIG. 2 is a waveform diagram for explaining the operation of the converter according to the present invention, and FIG. It is a figure showing other examples. E: DC power supply, T: Transformer, D1, D2: Diode C1-C5: Capacitor, L: Inductor, R1-R16:
... resistor U1 ... converter drive circuit, U2 ... operational amplifier, PC ...
Photocoupler Q1 …… FET, Q2, Q3 …… PNP transistor Q4, Q5 …… NPN transistor, t1, t2 …… Output terminal Vref… Reference voltage source, RL …… Load

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-61-262081 (JP, A) JP-A-51-13515 (JP, U)

Claims (2)

(57) [Claims] A DC power supply, a transformer, a switching element, and a converter driving circuit for driving the switching element on and off, comprising a voltage stabilizing terminal, and a pulse according to a voltage level of the voltage stabilizing terminal. A converter drive circuit for generating a width modulation signal output, rectifying and smoothing the voltage of the secondary winding of the transformer to obtain a DC output voltage, detecting the DC output voltage, and comparing it with a reference voltage. A converter for providing the error signal obtained as described above to the voltage stabilizing terminal of the converter driving circuit via an insulating means, comprising an integrating circuit for integrating the pulse width modulation signal of the converter driving circuit, and A converter configured to superimpose the obtained minute triangular wave on a voltage stabilizing terminal of the converter drive circuit. 2. The integration circuit according to claim 1, wherein a resistor and a capacitor are connected in series between a voltage stabilizing terminal of the converter drive circuit and a common line, and both ends of the capacitor are driven by the pulse width modulation signal output. The converter according to claim 1, wherein the semiconductor switching elements are connected.