JP2544550Y2 - rectifier - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rectifier capable of reducing the power loss of a diode.

[0002]

2. Description of the Related Art When an alternating current is converted to a direct current by a diode, a power loss occurs due to a forward voltage drop of the diode. In order to reduce this power loss, an insulated gate field effect transistor (FE
T) is connected, and an on-control signal is applied to the FET during the forward conduction period of the diode to reduce the forward drop of the diode.

[0003]

[Problem to be solved by the invention] However, one FET
Connected in parallel with a diode
Couldn't be smaller in minutes.

Therefore, an object of the present invention is to improve cost.
Control to reduce the forward voltage drop.
It is to provide a sink.

[0005]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention incorporates diodes connected in parallel with each other and each connected in parallel between drain sources.
A plurality of field effect transistors,
Provided for each of the field effect transistors
Not selected from the plurality of field effect transistors
Current detection means provided only for the
Current detecting means for forward biasing the diode.
Between the plurality of field effect transistors during this period.
And a control circuit for simultaneously applying an ON control signal to the
It relates to a rectifier. In addition, as shown in claim 2
Alternatively, the current detection means can be a current detection resistor.

[0006]

According to the present invention, the following effects can be obtained. (B) Multiple field-effect transistors with built-in diodes
By connecting in parallel, the combined resistance of this parallel connection circuit
Rectifier with small forward voltage drop
Can be provided. (B) To detect the forward bias period of the diode
Current detection means for multiple field effect transistors.
Do not provide each and only provide
Multiple field-effect transistors based on the
Simultaneous on-control allows multiple field-effect transistors
Compared with the case where current detection means is provided for each of
Cost can be reduced. Further, according to claim 2
In the case of the plan, since the current detection means is a current detection resistor,
Each field effect transistor has a current detection resistor
Or the total power of multiple field-effect transistors.
It is possible to reduce the power loss in the current detection resistor in comparison with the case of detecting the flow.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a switching power supply including a rectifier according to an embodiment of the present invention will be described with reference to FIG. FIG.
Has a switching element 4 connected to a DC power supply 1 via a primary winding 3 of a transformer 2. The switching element 4 is ON / OFF controlled by the control circuit 5 so that the output voltage becomes constant. Transformer 2 2
An output rectifying / smoothing circuit including first and second rectifiers 7 and 8, a reactor 9, and a capacitor 10 is connected to the secondary winding 6. That is, the first rectifier 7 is connected in series to the output line, the second rectifier 8 is connected between a pair of output lines, the reactor 9 is connected in series to the output line, and the capacitor 10 is connected to the output terminals 11 and 12. Connected between them.

The first and second rectifiers 7 and 8 each include a diode 13, first and second FETs 14 and 15, a current detection resistor 16, and an operational amplifier (operational amplifier) 17, both of which are the same. It has a circuit configuration. The first and second FETs 14 and 15 are insulated gate type FETs each having a substrate connected to a source, and include FET portions Q1 and Q2 as switching elements and built-in diodes D1 and
D2. The built-in diodes D1 and D2 are connected in parallel in the reverse direction between the drain and source of the FET. A diode 1 is connected between the anode terminal A and the cathode terminal K.
3 and the first and second FETs 14 and 15 are connected in parallel with each other. A resistor 16 as a current detector is used to detect the forward current of the diode D1.
Are connected in series. A pair of terminals of the operational amplifier 17 are connected to both ends of the resistor 16, and output terminals are first and second terminals.
Are connected to the gates of the FETs 14 and 15, respectively. Although not shown, a power supply circuit for the operational amplifier 17 is of course also provided.

The first and second rectifiers 7, 8 are each formed by a single semiconductor chip into an IC (integrated circuit) structure so that they can be handled as one component. Therefore, connection of the first and second rectifiers 7 and 8 to the circuit can be easily achieved.

The first rectifier 7 is connected to the secondary winding 6 of the transformer 2.
When a voltage is generated in a direction for forward biasing the internal diodes D1, D2 of the first and second FETs 14, 15,
A forward current starts flowing through the external diode 13 and a forward current also flows through the external diode 13. As a result, a voltage drop occurs in the resistor 16, and a voltage corresponding to the voltage between both terminals of the resistor 16 is obtained from the operational amplifier 17, and is applied to the gates of the first and second FETs 14 and 15 as an ON control signal, The FET portions Q1 and Q2 are turned on. As a result, a parallel circuit of the FET portions Q1 and Q2 and the built-in diodes D1 and D2 is formed, the on-resistance and the voltage between both ends of the first and second FETs 14 and 15 are reduced, and the power loss is reduced.

The current detecting resistor 16 includes a plurality of FETs 14,
Since only one of the external diode 15 and the external diode 13 is connected in series, the current flowing through the resistor 16 is relatively small and the power loss is small. In the embodiment, two Fs
Although the ETs 14 and 15 are connected in parallel, if the number of FETs is further increased, the ratio of the power loss in the resistor 16 to the whole becomes further smaller.

As apparent from the above description, in this embodiment, the FE is detected based on the detection of the forward current flowing through the diode D1.
Since the ON control signal is applied to T14 and T15, it is possible to drive the FETs 14 and 15 ON only accurately during the forward conduction period of the diode D1. Rectification with low loss can be achieved.

[0013]

[Modifications] The present invention is not limited to the above-described embodiment, and for example, the following modifications are possible. (1) The diode 13 can be omitted from the rectifier 7 of FIG. (2) Instead of the resistor 16 in FIG. 1, a sensor for magnetically detecting the current is arranged along the current path of the diode D1, thereby detecting the forward current of the diode D1 and based on the detected output. Alternatively , an on-control signal may be formed by a gate control circuit and applied to the gates of the FETs 14 and 15 . (3) The rectifier of the present invention can be used not only for the output rectifier circuit of the switching regulator but also for various rectifier circuits.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a switching regulator according to an embodiment of the present invention.

Claims (2)

(57) [Scope of request for utility model registration] 1. The method according to claim 1 , further comprising the steps of:
A diode connected in parallel between the drain and source
A plurality of field effect transistors ,
Provided for all of the field effect transistors
Not selected from the plurality of field effect transistors.
A current detecting means provided with respect to only those to detect the forward bias period of the diode by said current detecting means, said plurality of field effect tiger this period
Rectifier and a control circuit for applying an ON control signal simultaneously to Njisuta. 2. The current detection means is a current detection resistor.
The rectifier according to claim 1, wherein: