JPH0626472B2 - DC power supply - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a DC power supply device that employs a plurality of DC-DC converters, and more particularly to noise reduction in phase with a switching frequency.

[Prior Art] Conventionally, when a predetermined stabilized DC voltage Vout1,2, ..., n is supplied to a load using a plurality of DC-DC converters, a switching frequency is used in synchronization and a beat It prevents the occurrence. Further, by mounting a filter circuit, it is possible to suppress the leakage of the signal related to the switching frequency fsw to the upstream side and reduce the conductive noise.
(Electromagnetic interference) measures are taken.

However, when the number of DC-DC converters increases, noise also increases. Therefore, in order to suppress the noise level to a constant value,
For example, as disclosed in Japanese Utility Model Laid-Open No. 57-155985, there is known a technique of operating a switching element with a phase shift.

FIG. 6 is a circuit diagram of an apparatus in which two half bridge type converters are connected in parallel. In the figure, 10 is a half-bridge type converter, and 20 is a rectifying / smoothing circuit, and there are two systems corresponding to the half-bridge type converter 10 one-to-one. Reference numeral 30 denotes a control circuit, which is a DC-DC converter that outputs the input voltage Vin as the stabilized voltages Vout1, 2 as a whole. Reference numeral 40 is a filter for removing a signal component related to the switching frequency fsw, and in the half-bridge converter, 0.5 fsw is the basic frequency.

Next, details of the half bridge converter 10 will be described. One end of the capacitor C11 is connected to the + side of the input voltage Vin, the other end is connected to the capacitor C12, and the other end of the capacitor C12 is connected to one side of the input voltage Vin. The switch element SW11 is composed of, for example, a transistor, the collector of which is connected to the + side of the input voltage Vin, the emitter of which is connected to the collector of the switch element SW12, while the emitter of the switch element SW12 is the input voltage Vin. It is connected to one side. An ON / OFF control signal is supplied from the control circuit 30 to the bases of the switch elements SW11 and SW12. Further, since the switch elements SW11,12 generate heat, heat sinks HS11,12 are attached for cooling, and a capacitance is formed between them. This capacitance is also called parasitic capacitance, and is 40 pF, for example. The diodes D11,12 mounted between the collectors and emitters of the switch elements SW11,12 have the purpose of preventing reverse current flow. One end of the primary side of the transformer T1 is coupled to the connection point of the switch elements SW11,12, and the other end is coupled to the connection point of the capacitors C11,12. The secondary side of the transformer T1 is connected to the rectifying / smoothing circuit 20 so as to stabilize the voltage Vou.
Output t1.

Regarding the second system of the half-bridge converter 10, the subscripts 11 and 12 added to the above-mentioned components are 21 and 22 respectively.
And trans T1 to T2.

The operation of the apparatus thus configured will be described below. 7th
FIG. 8 is a circuit diagram of a main part showing a signal position, FIG. 8 is a signal waveform diagram, and ~ are control signals of the control circuit 30, ~ are potentials at one end f1,2 of the transformers T1,2, and the scale is switching. The time (I / fsw) corresponds to the frequency fsw.

One switching element SW of half-bridge converter
Reference numerals 11 and 12 are alternately turned on according to the control signal of the control circuit 30, and the output signals are driven in the same phase (this is because of the relationship with the counterpart converter driven in the opposite phase).
The other switch element SW of the half-bridge converter
Reference numerals 21 and 22 are alternately turned on with respect to the control signal of the control circuit 30, and the output signals are driven in reverse phase. In order to do this, the switch elements SW11, 22 can be turned on in the same section, and the switch elements SW12, 21 can be turned on in a section opposite to this. As a result, the terminal voltage f1 on the switch element SW11,12 side of the transformer T1
Then, the terminal voltage f2 on the switch element SW21,22 side of the transformer T2 has a reverse phase.

As shown in FIG. 7, there is a capacitor C1 between the switch elements SW11 and SW12 and the heat sink HS1, and a signal I of half the switching frequency 0.5 fsw is present due to capacitive coupling.
c1 flows to the ground. Similarly, switch element SW
21,22 There is a capacitor C2 between the heat sink HS2 and half of the switching frequency is 0.5 due to capacitive coupling.
The signal Ic2 of fsw flows to the ground. Therefore, the common current Icom flowing to the ground is given by the following equation.

Icom = Ic1 + Ic2 (1) The common current Ico
m decreases.

FIG. 9 is a circuit diagram of a main part of an apparatus in which two on / on converters are connected in parallel. FIG. 10 is a waveform diagram for explaining the control state of the apparatus of FIG. 9, (A) in-phase operation, and (B) showing anti-phase operation.

Transformer and switch element SW in the on / on converter format
And one-to-one. Therefore, as compared with the case where the two converters are operated in synchronization, the common current Icom due to the capacitive coupling between the switch element SW and the heat sink HS can be reduced when operating in reverse phase. The frequency of the output signal matches the switching frequency fsw.

[Problems to be solved by the invention]

By the way, the following four types of converters are typical, and are appropriately used according to the output capacity for reasons such as mounting, component cost and conversion efficiency.

on / off type: 50 W or less on / on type: about 50 to 150 W Half bridge type: about 200 to 300 W Full bridge type: about 300 W or more On the other hand, in power supply applications, for example, 250 W for 5 V
There is an application where it is necessary and 100 W is required for 12V. In such a case, it is preferable to use a half bridge type for the main output and an on / on type for the slave output, rather than a common converter type for each output voltage. However, if the converter type is different, the switching frequency will be the same and the drive phase will be 18
There is a problem that even if it is shifted by 0 degree, the noise reduction effect cannot be sufficiently obtained.

The present invention solves such a problem, and an object of the present invention is to provide a DC power supply device in which common mode noise due to switching is small even when the converter type is different depending on the output capacitance.

[Means for solving problems]

In the present invention which achieves such an object, a plurality of transformers (T) whose primary side is connected to a DC power source (Vin) and whose secondary side is connected to a load, and which are mounted on the respective primary sides of these transformers and controlled A switch element (S) that is turned on and off by a signal, a grounded heat sink (HS) that cools these switch elements, and a frequency component related to the control signal that is inserted between the primary side of the transformer and the power supply. A direct-current power supply device having a filter for removing the above is configured as follows.

That is, for one of the transformers, a half-bridge converter in which either one of the first switch element (S11) and the second switch element (S12) is turned on or both are controlled to be off For the other transformer, the on / on converter having the third switching element (S2) is driven at half the operating frequency, and the output signal frequency of these converters is set to the operating frequency. It is provided with a control circuit (30) for supplying control signals which are matched in half and output in opposite phases.

The frequency component associated with the control signal flowing to the ground via the heat sink by capacitive coupling with the switch element is reduced by operating in reverse phase of these converters.

[Action]

The components of the present invention have the following functions. Due to the capacitive coupling between the switch element and the heat sink, the frequency components associated with the control signal flow to ground. Therefore, a control signal is output to a plurality of DC-DC converters that are a combination of a half-bridge converter and an on / on converter so that the output signals have opposite phases, so that the frequency components related to the control signal flowing to the ground are output. Is canceled and decreases. As a result, the capacity of the filter is small.

〔Example〕

 The present invention will be described below with reference to the drawings.

FIG. 1 is a circuit diagram of an essential part showing an embodiment of the present invention, in which one is a half-bridge converter and the other is an on / on converter. When the frequency of the output signal is based on the switch frequency fsw, the half bridge converter has a half frequency and the on / on converter has the same frequency, which are different from each other. Therefore, the control signal supplied from the control circuit is turned on alternately for the switch elements SW11, 12 constituting the half-bridge converter, and is turned on / off.
The original switching frequency fsw for the on converter
The switch element SW2 is driven by half of the above.

FIG. 2 is an explanatory diagram of output waveforms. The output waveform is half the switching frequency, 0.5 fsw. Therefore, the switch element SW2 is turned on at the timing when the switch element SW11 is turned on so that the converters have opposite phases.

FIG. 3 is a configuration block diagram showing another embodiment of the present invention. In the above-mentioned embodiment, the case where the number of DC-DC converters is two is shown, but the same can be done even when the number of DC-DC converters is three or more.
In this case, the DC-DC converter is driven in phase and the DC-DC converter is driven in reverse phase. This partition is preferably chosen to minimize the common current Icom. For example, if Ic1>Ic2> Ic3, the first
It is preferable that the set be Ic1 and the second set be Ic2 and Ic3.
The current Ic based on the capacitive coupling is the switching frequency fsw.
And the capacitance between the switch element SW and the heat sink HS.

Next, the results of experiments conducted by the inventor of the present invention will be shown. FIG. 4 is a relationship diagram between the drive phase and the noise generation amount. Here, two 250 W DC-DC converters are used, the in-phase drive is indicated by A, and the anti-phase drive is indicated by B, for comparison with single operation. Fig. 5 shows the noise measurement results for each frequency. Comparing drive B with drive A, the noise level is 13 dB less in the fundamental wave, and there is no effect in the secondary wave, but higher-order waves higher than the third Also, it is reduced by 4 to 8 dB.

〔The invention's effect〕

As described above, according to the present invention, when the half bridge type and the on / on type converter are combined in parallel according to the load power, the switching frequency becomes half of the half bridge type in the on / on type converter. Since the drive is performed with the phase shifted by 180 degrees, the common current Icom is reduced and the noise is reduced. Therefore, there is an effect that the filter can be downsized and the component cost can be reduced.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an essential part showing an embodiment of the present invention, in which one is a half-bridge converter and the other is an on / on converter, and FIG. 2 is an explanatory diagram of output waveforms.
FIG. 3 is a block diagram showing the configuration of another embodiment, FIG. 4 is a diagram showing the relationship between drive phase and noise generation amount, and FIG. 5 is an example of experimental results. FIG. 6 is a circuit diagram in which half bridge converters are connected in parallel, FIG. 7 is a circuit diagram of a main part showing signal positions, and FIG. 8 is a signal waveform diagram. FIG. 9 is a circuit diagram of a main part in which on / on converters are connected in parallel, and FIG. 10 is a waveform diagram for explaining a control state of the apparatus of FIG. C ... Capacitor or coupling capacitance, HS ... Heat sink, SW ... Switching element, T ... Transformer, Icom
...... Common current.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasunobu Iwata 2-9-32 Nakamachi, Musashino-shi, Tokyo Yokogawa Electric Co., Ltd. (56) References JP-A-59-132772 (JP, A) JP-A-SHO 53-29531 (JP, A) Actual opening 57-155985 (JP, U) Actual opening 60-147986 (JP, U) Actual opening 59-141489 (JP, U) Actual opening 60-141691 (JP, U)

Claims (1)

[Claims] 1. A plurality of transformers (T) each having a primary side connected to a DC power source (Vin) and a secondary side connected to a load, and switches mounted on respective primary sides of these transformers and turned on / off by a control signal. The element (S) and a grounded heat sink (H) that cools these switch elements.
S) and a DC power supply device having a filter inserted between the primary side of the transformer and the power supply to remove frequency components related to the control signal, wherein one of the transformers has a first switch element ( S1
One of the 1) and the second switch element (S12) is alternately driven at a predetermined operating frequency to drive a half-bridge converter in which either one is turned on or both are turned off, and the other transformer is Third switch element (S
A control circuit (30) for driving an on / on converter having 2) at half of the operating frequency, matching the output signal frequencies of these converters at half of the operating frequency, and supplying control signals for outputting in opposite phases. And a frequency component associated with a control signal flowing to the ground through the heat sink by capacitive coupling with the switch element is reduced by operating these converters in reverse phase. .