JP2000224855A - Dc-to-dc converter circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a DC/DC converter circuit which is formed as an input/ output insulation type and which can perform zero-voltage switching operation of a main switching element. SOLUTION: From among a group of main switching elements in a bridge circuit 11, two main switching elements Q1, Q2 in positions in which a DC power supply is short-circuited are turned on, a current flows into an inductor 16, and energy is stored. The stored energy is discharged while a primary current is made to flow to the primary winding of an output transformer 12, when two main switching elements Q2, Q3 positioned diagonal are turned on. Then, two main switching elements Q2, Q4 in other short-circuit positions are turned on, energy is stored again in the inductor 16, and the two main switching elements Q1, Q4 in another diagonal positions are then turned on, in such a way that the direction of the primary current is directed in the opposite direction. In addition, before the two main switching elements in the diagonal positions are turned on, an auxiliary switching element QA is turned on, by using the reactor energy of an auxiliary winding 18, the electric charge of the main switching elements results in being pulled out, and a zer-voltage switching operation is performed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a DC device for reducing loss by realizing zero voltage and zero current switching.
A DC converter circuit;

[0002]

2. Description of the Related Art A DC-DC converter circuit of this kind includes:
There is an advantage that there is little high-frequency disturbance, and it is also called a so-called soft switching regulator. As an example, an example described in “IEICE Technical Report” published by the Institute of Electronics, Information and Communication Engineers will be described. As shown in FIG. 12, a resonance capacitor Cr and a reverse diode D2 are connected in parallel between the collector and the emitter of the main switch element Q1, and a series circuit of an auxiliary switch element QA2, a transformer T1 and an auxiliary inductor L2 is connected in parallel. The secondary side of the transformer T is connected to an output line via a diode D3.

In this circuit configuration, when the main switch element Q1 is turned on, a current IL flows through the main inductor L1 to store energy. When the main switch element Q1 is turned off, the resonance capacitor Cr including the parasitic capacitance of the main switch element Q1 is charged with a constant current by the current IL. Therefore, the main circuit voltage (collector-emitter voltage) of the main switch element Q1
Rises relatively slowly, and the switching loss when the main switching element Q1 is turned off is extremely small. After the main switching element Q1 is turned off, the energy stored in the main inductor L1 is released to the load through the diode D1, and the auxiliary switching element Q2 is turned on immediately before the main switching element Q1 is turned on next. Then, a part of the current IL from the main inductor L1 is transferred to the auxiliary inductor L2 and the transformer T.
Shunting through the primary winding and the auxiliary switch element Q2, and the electric charge accumulated in the parasitic capacitance of the main switch element Q1 and the resonance capacitor Cr is discharged through the route of L2, T, Q2. At this time, the current flowing through the auxiliary switching element Q2 gradually rises as a resonance current, so that the switching loss in the auxiliary switching element Q2 is extremely small. When the voltage between the main circuits of the main switch element Q1 becomes zero, a gate signal is applied to the main switch element Q1 to perform a zero voltage switching (ZVS) operation. In addition, the auxiliary switching element Q2 performs a zero current switching (ZCS) operation of turning off after the resonance current flowing therethrough becomes zero.

In this configuration, each switching element Q1, Q2
Perform the ZVS and ZCS operations, so that there is an advantage that switching efficiency can be suppressed and high efficiency and low noise can be achieved.

[0005]

However, in the above configuration, the input and output are in a non-insulated state, which is not preferable for safety. In this regard, it is conceivable to connect an insulated converter in tandem with the above-mentioned boost converter, but this requires two converters to be controlled simultaneously, which complicates the circuit and increases efficiency and reliability. It can lead to a decline.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a DC-DC converter circuit which is made of an input / output insulation type, has high safety, and is excellent in efficiency.

[0007]

In order to achieve the above object, a first aspect of the present invention is to connect four main switch elements in a full bridge type and to connect between four main switch elements at diagonal positions. A bridge circuit having an output transformer connected thereto, an inductor interposed in a power supply circuit from the DC power supply to the bridge circuit, and a main switch element group of the bridge circuit at a position where the DC power supply is short-circuited. By turning on the two main switch elements and then turning on the two main switch elements at diagonal positions, the operation of passing the primary current through the primary winding of the output transformer reverses the direction of the primary current alternately. A switching control circuit for controlling a switching operation of each main switch element so as to change in a direction; and a DC current connected to a secondary winding of the output transformer and applied to a load. And a supply rectifier circuit DC-
In the DC converter circuit, an auxiliary winding is provided on the inductor, and the auxiliary switch element is connected in series with the auxiliary winding and the diode, and is connected in parallel to the two main switch elements at a position where the DC power supply of the bridge circuit is short-circuited. It is characterized in that the auxiliary switch element is turned on prior to the turn-on of the main switch element so that the electric charge of the main switch element is extracted using the reactor energy of the auxiliary winding.

According to this configuration, the switching control circuit turns on the two main switch elements of the group of main switch elements of the bridge circuit at the position where the DC power supply is short-circuited, so that the power supply circuit for the bridge circuit is turned on. A current flows through the interposed inductor and energy is stored. The stored energy is released by the primary current flowing through the primary winding of the output transformer by the switching control circuit turning on the two main switch elements at the diagonal positions of the bridge circuit, and then another short-circuit position Are turned on, energy is again stored in the inductor, and then the two main switch elements at different diagonal positions have the primary current directions opposite to those described above. As a result, the reverse current flows alternately in the output transformer, and is supplied from the secondary winding to the load through the rectifier circuit.

At this time, the auxiliary switch elements are turned on prior to the turn-on of the two main switch elements at the diagonal positions, so that the charges of the main switch elements are extracted using the reactor energy of the auxiliary winding. That is, zero voltage switching is performed.

A second aspect of the present invention is characterized in that, in the first aspect, the switching control circuit is configured to perform PWM control on each main switch element of the bridge circuit. Further, the invention of claim 3 is based on claim 1 or 2
Is characterized in that a ringing preventing capacitor is provided between two main switch elements of the main switch element group of the bridge circuit at a position where the DC power supply is short-circuited. Ringing due to the influence of the leakage inductance of the output transformer due to opening and closing is suppressed.

[0011]

As described above, the DC-DC of the present invention
According to the converter circuit, since each main switch element of the bridge circuit performs a zero voltage switching (ZVS) operation, switching loss can be significantly reduced,
Efficiency can be improved. Further, since the bridge circuit is provided with the output transformer, there is an advantage that the input / output insulation type is configured and the safety is high.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to an in-vehicle charging device for charging a power battery of an electric vehicle will be described below. As shown in FIG. 1, the overall configuration is such that a household power supply 1 of, for example, AC 200 V is connected to a vehicle via a connector device 2.
The vehicle is provided with an electromagnetic wave filter 3, a rectifier circuit 4 for rectifying alternating current from the home power supply 1, and a step-up DC-DC converter circuit 10 according to the present invention. The power battery 5 corresponding to the applied load is charged.

The details of the DC-DC converter circuit 10 are shown in FIG. 2, for example, four main switching elements Q1 to Q1 each comprising a MOS gate input type bipolar transistor.
4 is provided with a bridge circuit 11 which is connected to a full bridge type. The bridge circuit 11 is provided with an output transformer 12 for high frequency, and a primary winding 12p is connected between diagonally located ones of the four main switch element groups. A rectifier circuit 13 formed by connecting diodes in a full bridge is connected. The DC output of the rectifier circuit 13 is connected to the battery 5 together with the smoothing capacitor 14.

In FIG. 2, the output of the rectifier circuit 4 on the input side is symbolized as a DC power supply 15, and an inductor 16 is interposed in a power supply circuit from the DC power supply 15 to the bridge circuit 11. .

The inductor 16 has a core 17
Are wound, and the turn ratio thereof (the number of turns n1 of the energy storage main winding 16 / the number of turns n2 of the auxiliary winding 18) is 2/1 here. The auxiliary winding 18 forms a series circuit with the diode 19, the auxiliary inductor 20, and the auxiliary switch element QA so that the main winding of the inductor 16 has the polarity shown in the drawing. It is connected between the input circuits of the circuit 11. The auxiliary switch element QA is also a MOS transistor input bipolar transistor, and is connected in parallel with the diode 19 to each of the main switch elements Q1 and Q2 of the bridge circuit 11 in a forward direction. Note that a capacitor 21 (for example, about 0.1 to 0.47 μF) for preventing ringing is provided between the two main switch elements Q1 and Q3 of the main switch element group of the bridge circuit 11 which is located at a position where the DC power supply 15 is short-circuited. Is provided. The switching control circuit 22 for controlling the gates of the main switch elements Q1 to Q4 of the bridge circuit 11 is connected to the main switch elements Q1 to Q4 as described below.
To Q4 are controlled to open and close by PWM control, and the switching frequency is set to, for example, 35 kHz.

Next, the operation of the above configuration will be described. This circuit has eight operation modes, Mode 1 to Mode 8, during one switching period TS, and these are shown in order in the circuit state diagrams ideally shown in FIGS. In the mode 1 shown in FIG. 3, two main switch elements Q1 and Q3 at a position where the DC power supply 15 is short-circuited are turned on together with the main switch element Q3 in the main switch element group of the bridge circuit 11, and the DC power supply 15 is short-circuited, energy is stored in the inductor 16, and at time t1, the main switch element Q1 is turned off and the mode transits to mode 2.
In this state, since a reverse voltage is generated in the inductor 16, the sum of the voltage of the DC power supply 15 and the voltage of the DC power supply 15 is applied to the primary winding 12 p of the output transformer 12, so that the primary current itr 1 flows and is accumulated in the inductor 16. Energy is supplied to the battery 5 as a load via the output transformer 12 and the rectifier circuit 13 (see FIG. 4).

At the end of the mode 2, while the main switch elements Q2 and Q3 are turned on, the auxiliary switch element QA is turned on prior to the main switches Q4 and Q1 and transits to the mode 3 shown in FIG. Here, the voltage generated in the auxiliary winding 18 of the inductor 16 is applied to the auxiliary inductor 20 connected in series with the auxiliary switch element QA, and the current increases substantially linearly. As a result, the current of iQA-iL1 flows in the circuit in the direction shown in FIG. 5, and the charge stored in the main switching elements Q1 and Q4 is extracted. If energy remains in the auxiliary inductor when the CE voltage of the main switching elements Q1 and Q4 reaches zero, current flows through the parasitic diodes of the main switching elements Q1 and Q4. The switching control circuit 22 outputs the main switching element Q4 after all the electric charges of the main switching element Q4 are extracted and the CE voltage becomes zero.
4 is turned on, zero voltage switching of the main switching element Q4 is realized, and the mode shifts to mode 4.

In this mode 4, the main switching elements Q1, Q1,
Although Q2 and Q4 are on, energy is accumulated in the inductor 16 by the two main switch elements Q2 and Q4 at the position where the DC power supply 15 is short-circuited. The difference from the mode 1 is that the anode current iQA flows through the diode 19 connected in series to the QA (see FIG. 6). This anode current iQ
A rapidly decreases, and when it becomes zero (time t4)
Then, the diode 19 is turned off, and the mode shifts to mode 5.

In mode 5, the DC power supply 15 is short-circuited through the inductor 16 as shown in FIG. 7, so that energy is accumulated in the inductor 16 and the main switch element Q2 is turned off at time t5, thereby causing mode 6 to occur. Move to In the mode 6, the reverse voltage is generated in the inductor 16 as in the mode 2, but the switching control circuit 22
Turns on the main switch elements Q1 and Q4, so that the sum of the voltage of the DC power supply 15 and the back electromotive force of the inductor 16 is applied to the primary winding 12p of the output transformer 12 in the opposite direction to the mode 2. A reverse primary current ip flows (see FIG. 8).

At the end of mode 6, as in mode 3, while main switch elements Q1 and Q4 are on, auxiliary switch element QA turns on prior to main switches Q2 and Q3, and the mode shown in FIG. 7 and the charges stored in the main switching elements Q2 and Q3 are extracted in the same manner as in the mode 3. Then, the switching control circuit 22 turns on the main switching element Q3 to perform zero-voltage switching after all the electric charges of the main switching element Q3 are extracted and the CE voltage becomes zero, and shifts to mode 8. As in the case of mode 4, the diode 19 is turned on to return to mode 1, and thereafter, the transition of modes 1 to 8 is repeated.

As described above, according to the present embodiment, the auxiliary switch element QA can perform zero voltage switching of the main switch elements Q1 to Q4, and the auxiliary switch element QA can perform zero current switching. Therefore, it is possible to increase the efficiency and improve the input power factor. In addition, since the bridge circuit 11 includes the output transformer 12, the bridge circuit 11 is an input / output insulated type and has high safety. Also,
In the present embodiment, in particular, the two main switch elements Q1, Q3
Since the small-capacity capacitor 21 is provided therebetween, ringing of the CE-to-CE voltage waveform of the main switch elements Q1 to Q4 due to the influence of the leakage inductance of the output transformer 12 can be suppressed.

The present invention is not limited to the embodiments described with reference to the above description and the drawings. For example, the present invention can be modified and implemented as follows, and these also belong to the technical scope of the present invention. (1) In the above embodiment, each switch element is constituted by a MOS gate input type bipolar transistor.
Of course, it may be constituted by an OSFET or a base input type bipolar transistor.

(2) In order to improve the input power factor, the current flowing through the inductor and the load is monitored, and the switching of the four main switching elements of the bridge circuit is performed so that a current similar to the AC voltage flows. May be controlled, and this function can be easily realized by a general-purpose power factor correction control IC.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment in which the present invention is applied to a vehicle-mounted charger of an electric vehicle.

FIG. 2 is a circuit diagram of a DC-DC converter circuit showing an embodiment of the present invention.

FIG. 3 is a circuit state diagram showing a state of mode 1 of the DC-DC converter circuit of the embodiment.

FIG. 4 is a circuit state diagram showing a state of mode 2 in the same manner.

FIG. 5 is a circuit state diagram showing a state of mode 3 in the same manner.

FIG. 6 is a circuit state diagram showing a state of mode 4 in the same manner.

FIG. 7 is a circuit state diagram showing a state of mode 5 in the same manner.

FIG. 8 is a circuit state diagram showing a state of mode 6 in the same manner.

FIG. 9 is a circuit state diagram showing a state of mode 7 in the same manner.

FIG. 10 is a circuit state diagram showing a state of mode 8 in the same manner.

FIG. 11 is a voltage / current waveform diagram of each part.

FIG. 12 is a circuit diagram showing an example of a conventional DC-DC converter.

[Explanation of symbols]

 5 ... Battery (load) 10 ... DC-DC converter circuit 11 ... Bridge circuit 12 ... Output transformer 13 ... Rectifier circuit 14 ... Smoothing capacitor 15 ... DC power supply 16 ... Inductor 17 ... Iron core 18 ... Auxiliary winding 19 ... Diode 20 ... Auxiliary Inductance 21: Capacitor for preventing ringing 22: Switching control circuit Q1 to Q4: Main switch element QA: Auxiliary switch element QA

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shuji Nakamura 1 Inakinomabacho, Nishinosho, Kisho-in, Minami-ku, Kyoto F-term in Nippon Battery Co., Ltd. 5H730 AA14 AA18 AS01 BB23 BB27 BB57 BB66 CC04 DD02 EE04 EE07 FG01

Claims (3)

[Claims] 1. A bridge circuit having four main switch elements connected in a full bridge type and having an output transformer connected between diagonally positioned main switch elements, and power supply from a DC power supply to the bridge circuit. Turning on two inductors interposed in a circuit and two main switch elements of the group of main switch elements of the bridge circuit at a position where the DC power supply is short-circuited, and thereafter, two main switch elements at diagonal positions A switching control circuit that controls a switching operation of each main switch element so that an operation of flowing a primary current to a primary winding of the output transformer by turning on the output transformer alternately changes the direction of the primary current. A rectifier circuit connected to a secondary winding of an output transformer and supplying a direct current to a load. An auxiliary winding is provided on the main switch, and the auxiliary switch element is connected in series with the auxiliary winding and the diode in parallel with the two main switch elements at positions where the DC power supply of the bridge circuit is short-circuited. A DC-DC converter circuit, characterized in that the auxiliary switch element is turned on before the element is turned on, thereby utilizing the reactor energy of the auxiliary winding to extract the electric charge of the main switch element. 2. The DC-DC converter circuit according to claim 1, wherein the switching control circuit performs PWM control on each main switch element of the bridge circuit. 3. A ringing preventing capacitor is provided between two main switch elements of the group of main switch elements of the bridge circuit which are located at positions where the DC power supply is short-circuited. DC-DC converter circuit.