JPS645988Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention is a multi-output power supply in devices that require multiple independent power supplies as control power supplies or power supplies for main circuit power element drive circuits, such as inverter devices. Related to DC-DC converter circuit.

[Technical background of the invention and its problems]

Inside an inverter device that controls a DC motor or an AC motor, there is a control block section that controls speed and current, and a drive block section that receives signals from this control block section and drives the main circuit power elements. , speed, position, etc., and each block requires a predetermined power supply.

Normally, it is rare that these power supplies can be used in common, and independent power supplies are required. In particular, the power supply for the drive circuit of the main circuit power element cannot be used unless it is a power supply that takes into consideration the mutual withstand voltage and insulation distance in relation to the main circuit voltage.

Conventionally, these power supply methods have been as follows:
A single commercial frequency driven power transformer with the required number of output windings was used on the output side, but with this method, the size and weight increased as the output capacity increased, creating an obstacle to miniaturizing the device. I was getting used to it.

As a measure to solve this problem, power supplies using switching power supplies or DC-DC converters have come into widespread use.

This type of power supply has a plurality of output stages, and is divided into two or three switching transformers to ensure voltage resistance and insulation distance between them. Furthermore, even if it is divided into two or three switching transformers like this,
Needless to say, it is smaller and lighter than the previous power transformer.

It is also well known that in order to make the switching transformer smaller and more efficient, the push-pull method and the bridge method are more effective than the forward method using a single transistor.

FIG. 1 is a block diagram of a conventional example configured in this manner.

1 is an input terminal for the drive signal (pulse), 2 is a signal voltage phase inverter, 1SW and 2SW are switches that turn off when the drive signal is applied and are no longer on.
3 is a DC power supply with voltage E, 1T and 2T are switching transformers each having a plurality of output windings and a central tap, 4, 5, 9, and 10 are primary side excitation windings,
6, 7, 8, 11, 12 are output windings, d1 to d1
0 is a diode.

In other words, two of 1T and 2T with central tap.
This is a multi-output converter circuit in which several switching transformers are connected in parallel, driven in push-pull by a set of drive circuits, and output is obtained from each output winding.

In FIG. 1, consider a certain point in time during the operation of the push-pull converter, for example, when switch 1SW is on and switch 2SW is off.

A simple equivalent circuit at this time is shown in FIG.

r ₁₁ , r ₁₂ , r ₂₁ , r ₂₂ and L ₁₁ , L ₁₂ , L ₂₁ , L ₂₂
are the primary excitation windings −, −, ′−′,
represents the internal resistance and inductance between '-'.

Here, for the sake of explanation, the primary currents flowing according to the output side loads of transformers 1T and 2T are i ₁ ,
i ₂ , and for convenience, i ₁ > i ₂ (1 formula).

If the voltages induced in the non-driving windings of the tap at the center are V ₁₂ and V ₂₂ respectively, then due to the primary currents i ₁ and i ₂ , Δv ₁ = r ₁₁ ×i ₁ … (2 equations) Δv ₂ = r ₂₁ ×i ₂ ... (Formula 3) A voltage drop occurs, and therefore the voltages V ₁₁ and V ₂₁ applied to the excitation inductance are respectively V ₁₁ = E-r ₁₁ ×i ₁ ... (Formula 4) V ₂₁ = E−r ₂₁ ×i ₂ …(Equation 5) becomes.

In a typical midpoint tap transformer, the primary winding ratio is 1:1. Therefore, V ₁₂ = V ₁₁ ... (Formula 6) V ₂₂ = V ₂₁ ... (Formula 7).

For simplicity, assuming that each internal resistance is the same, from (Equation 1), (Equation 2), and (Equation 3), Δv ₁ > Δv ₂ ... (Equation 8) Therefore, V ₁₁ = V ₁₂ <V ₂₁ = V ₂₂ ... (Formula 9) Due to the difference in the generated voltages of voltages V ₁₂ and V ₂₂ , (V ₁₂
<V ₂₂ ), the circulating current i ₀ shown by the broken line in FIG. 2 flows as i ₀ =V ₂₂ −V ₁₂ /r ₁₂ +r ₂₂ (Equation 10).

Normally, switching transformers and the like have a small internal resistance of, for example, about 10 to 20 mΩ in order to increase their efficiency. Therefore, even if a slight voltage difference occurs, a large circulating current flows.

Letting the generated losses be ΔP _(1T) and ΔP _(2T) , respectively, 1T side loss ΔP _(1T) = i ₀ ² × r ₁₂ ... (formula 11) 2T side loss ΔP _(2T) = i ₀ ² × r ₂₂ ...(Equation 12) Unnecessary loss occurs, which reduces the output capacity of the switching transformer itself.

For convenience, the condition is that the internal resistance is the same, but the condition is not limited to this, and the transformer 1T,
If there is a difference in the voltage induced on the non-drive winding side of each 2T, a phenomenon occurs in which this circulating current flows in all cases.

In addition to being caused by the magnitude of the primary current that flows depending on the output load, this may be due to slight differences in the winding ratio from the center tap of each transformer, or differences in internal resistance between transformers with different capacities. This can be attributed to.

For this reason, it is difficult to predict the magnitude of the 1T side loss ΔP _(1T) and 2T side loss ΔP _(2T) in advance, and in the conventional example, the capacity of the switching transformer itself is larger than the originally required capacity. However, there may be cases where the result is still not completely satisfactory.

[Purpose of invention]

The present invention overcomes the difficulties of the conventional example and provides a multi-output DC-DC converter circuit in which one master transformer with a center point tap and a plurality of slave transformers without a center point tap are connected in parallel. is its purpose.

[Summary of the idea]

The present invention is configured to connect multiple switching transformers in parallel, each of which has a center tap on the primary input side, and drive the transformer in an open loop with a 50% duty using a push-pull method using one set of drive circuits to obtain multiple outputs. In the DC-DC converter circuit,
In order to prevent unnecessary circulating current from flowing due to the parallel connection, a master transformer with one center point tap and multiple slave transformers without center point taps are connected in parallel, which reduces the circulation. Multi-output eliminates current and prevents switching transformer output reduction due to undesired heat generation
This is a DC-DC converter circuit.

[Example of idea]

A block diagram showing the circuit configuration in one embodiment of the present invention is shown in FIG.

The same reference numerals represent the same or corresponding parts in all drawings.

1T is a master transformer having a plurality of output windings 6, 7, 8, and the primary input side (windings 4, 5) has a center point tap.

3T is a slave transformer which has a smaller capacity than the master transformer 1T and has a plurality of output windings 11 and 12, and does not have a center tap on the primary side.

The resistance of the primary winding 13 of the slave transformer 3T is
Assuming that r ₂ is the inductance, L ₂ is the inductance, and i ₂ ' is the current that flows depending on the load, the simplified equivalent circuit shown in FIG. 4 is shown in accordance with FIG. 2.

(Formula 2), (Formula 4), (Formula 6) and V ₂ = V ₁₂ +E ... (Formula 13), the voltage applied to the slave transformer 3T is determined by the fluctuation factor V ₁₂ due to the output side load of the master transformer 1T. However, as mentioned earlier, the internal resistance of the switching transformer itself is small,
The effect of this voltage drop on the output voltage of the slave transformer 3T is small.

Generally, this kind of open-loop DC-DC
The required accuracy for the output side voltage obtained from the converter is such that the fluctuation range due to the fluctuation factor V ₁₂ due to the load of the master transformer 1T explained earlier is negligible, and the heat generation due to the circulating current seen in the conventional example is negligible. Therefore, a decrease in the rated output of the switching transformer itself becomes a problem from a usage standpoint.

In addition, the loss ΔP _(1T) of the resistance r ₁₂ in the master transformer 1T due to the current i ₂ ′ flowing in the slave transformer 3T is calculated as ΔP _(1T) = i ₂ ′ ² × r ₁₂ (Equation 14), which is conventional Since the unbalanced voltage shown in the example does not include the uncertain element that the unbalanced voltage is unstable, the input capacitance of the master transformer 1T may be determined in advance by including the generated loss of ΔP _(1T) .

As a specific input capacity, slave transformer 3
Since the applied voltage of T is doubled, 1/2 of the input capacitance of the slave transformer itself is transferred to the master transformer 1T.
This will be supplied by the non-drive winding.

In this way, it is composed of a master transformer 1T having one midpoint tap and a plurality of slave transformers 3T without a midpoint tap, and the master transformer 1
By selecting the input capacitance of T to be greater than the sum of its own output capacitance equivalent and 1/2 of the total input capacitance of all the slave transformers 3T connected in series, it is possible to eliminate the parallel connection seen in conventional examples. can solve the problems.

This embodiment (Fig. 3) shows the case where there is one master transformer 1T and one slave transformer 3T, but if two or more slave transformers 3T are used, they can be connected in the same way without any problem. is obvious.

[Effect of idea]

Thus, according to the present invention, it can be used for control or main element drive circuits such as inverter devices, etc.
In cases where multiple independent power supplies are required and the set output cannot be configured with a single switching transformer, a compact and reliable power supply can be configured without unnecessary capacity increase, and this is an ideal solution in the field. It has great benefits.

[Brief explanation of drawings]

Fig. 1 is a block diagram of the conventional example, Fig. 2 is a simplified equivalent circuit diagram during its operation, Fig. 3 is a block diagram showing the circuit configuration in an embodiment of the present invention, and Fig. 4 is a simplified equivalent circuit diagram during its operation. It is an equivalent circuit diagram. 1... Drive signal input terminal, 2... Signal voltage phase inverter, 3... DC power supply, 4, 5, 9, 10... 1
Next side excitation winding, 6, 7, 8, 11, 12... Output winding, d1 to d10... Diode, 1T... Master transformer (switching transformer), 2T
...Switching transformer, 3T...Slave transformer.

Claims (1)

[Claims for Utility Model Registration] 1. One master transformer having a midpoint tap on the primary input side and at least one slave transformer without a midpoint tap on the primary input side, while the master transformer does not have a midpoint tap. One or more slave transformers are connected in parallel to one end of the winding and the other end of the winding, and the master transformer is driven in an open loop with a 50% duty using the push-pull method, and output is obtained from each of the master transformer and slave transformer. A multi-output DC-DC converter circuit characterized by: 2. Scope of Utility Model Registration Claim 1, in which the input capacity of the master transformer is selected to be greater than or equal to the sum of the input capacity converted into its own output capacity and 1/2 of the total input capacity of all slave transformers connected in parallel. The described multi-output DC-DC converter circuit.