JP2000358367A - Low power consumption drive circuit at light load state for self-excited rcc - Google Patents

Abstract

PROBLEM TO BE SOLVED: To set a stable output voltage and reduce a power consumption in a light load state. SOLUTION: The base drive circuit of a main switching device 1 comprises a current detection circuit, consisting of a 2nd transistor 3 which detects a light load, a gate drive circuit consisting of a 1st transistor 2 which controls the on/off of the main switching device l and a multivibrator consisting of a 1st operational amplifier 26 and a 2nd operational amplifier 31, which are made to oscillate intermittently.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a switching power supply, and more particularly to a self-excited RCC power supply circuit.

[0002]

2. Description of the Related Art An RCC (Ringing Choke) according to the prior art is used.
Converter) The circuit configuration of the power supply circuit is as shown in the block diagram of FIG. In FIG. 3, a main switch element 102 is connected to one end of a primary coil 114, and a drive coil is connected between a gate terminal and a source terminal of the main switch element 102 via a series circuit including a capacitor 105 and a resistor 106. 115 are connected in parallel. A starting resistor 103 is connected in parallel between the gate terminal of the main switch element 102 and the other end of the primary coil 114, and a resistor 104 is connected in parallel between the gate terminal and the source terminal. RC
It constitutes the primary circuit of the C circuit. Further, a secondary coil 116 having a polarity different from that of the primary coil 114 is provided with a rectifier circuit composed of a diode 111 and a parallel capacitor 112 and a load resistor 113 to constitute a secondary output circuit.

[0003]

As a countermeasure for low power consumption during standby of a self-excited RCC power supply circuit, intermittent oscillation is performed by using a switch element having a slow operating characteristic to reduce power consumption. I was However, as shown in FIG. 2B, the amount of decrease in output voltage cannot be set, and
Power consumption was not stable either.

[0004]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned drawbacks of the prior art, and comprises a first transistor for controlling on / off of a main switch element and a light load detection circuit. A current detecting circuit comprising a second transistor to be connected in parallel to the driving coil, a multivibrator comprising a first operational amplifier for performing stable oscillation, and a second operational amplifier for providing intermittent oscillation of the multivibrator. did.

[0005]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a self-excited R according to the present invention.
FIG. 2 is a block diagram showing a circuit configuration of the CC, and FIG. 2 is a waveform diagram showing an output voltage waveform at a light load.

In FIG. 1, a main switch element 1 and a parallel capacitor 35 are connected to one end of a primary coil 12 in a self-excited RCC, and a secondary coil 17 having a different polarity from the primary coil 12 has A rectifier circuit including a diode 14 and a parallel capacitor 15 and a load resistor 16 are connected.

A drive coil 13 is connected between a gate terminal and a source terminal of the main switch element 1 by a capacitor 8 and a resistor 9.
Are connected in parallel via a series circuit consisting of: A resistor 5 is connected between the gate terminal and the source terminal of the main switch element 1 connected to one end of the starting resistor 4 and is connected in parallel. The collector terminal and the emitter terminal of the first transistor 2 for controlling ON / OFF of the main switch element 1 are connected in parallel between the gate and the source of the main switch element 1, and the base terminal is a connection point of the voltage dividing resistors 6 and 7. Connected to

A diode 20 and two voltage dividing resistors 21 and 2
2 is connected in parallel to the drive coil 13, and the second transistor 3 connected to the base terminal of the capacitor 23 connected in parallel to the resistor 22 forms a current detection circuit.

The inverting input terminal of the first operational amplifier 26 is
The non-inverting input terminal is connected to the ground side of the drive coil 13 via the capacitor 28, and the non-inverting input terminal is connected to the output terminal of the second operational amplifier 31 via the diode 30.
It is connected to the ground side of the drive coil 13 via a resistor 29. The output terminal is connected to the first
Is connected to the resistor 6 connected to the base terminal of the transistor 2 and connected to the inverting input terminal and the non-inverting input terminal via the resistors 25 and 27 to form a multivibrator.

The output terminal of the second operational amplifier 31 is connected to the non-inverting input terminal of the first operational amplifier 26 via the diode 30, and the non-inverting input terminal is connected to the collector terminal of the second transistor 3. Also, it is connected to a DC power supply 36 via a resistor 32. The inverting input terminal is connected to the ground side of the drive coil 13 via a resistor 34 and to a DC power supply 36 via a resistor 33.

Next, the operation of the first and second transistors and the first and second operational amplifiers will be described. Since the amount of charge to the capacitor 23 connected to the base terminal of the second transistor 3 is proportional to the load current, the capacitance of the capacitor under light load does not readily increase. Therefore, the output signal from the second transistor 3 operated by discharging the capacitor 23 becomes “0” when the load becomes light. The output signal from the second operational amplifier 31 that has input this signal to the non-inverting input terminal is input to the non-inverting input terminal of the first operational amplifier 26 that constitutes the multivibrator via the diode 30 and oscillates the multivibrator. Let it. In other words, the multivibrator that has stopped oscillating will intermittently oscillate according to the signal from the second operational amplifier 31. The output signal from the multivibrator is input to the base terminal of the first transistor 2 to control the on / off of the first transistor 2, and accordingly, the main switch element 1 is also controlled to be on / off. The voltage waveform diagram shown in FIG. 2A is a waveform of the output voltage V ₀ at the output terminal of the secondary coil 17, and has a drop of −ΔV due to intermittent oscillation.

[0012]

As described above, the self-excited RCC driving circuit for low power consumption under light load according to the present invention is composed of the first transistor for turning on / off the main switch element and the second transistor. And a second operational amplifier which intermittently oscillates a multivibrator comprising a first operational amplifier, and intermittently oscillates a multivibrator having a stable oscillation frequency at light load, so that a stable output is obtained. Voltage and low power consumption can be realized.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a drive circuit of a self-excited RCC according to the present invention.

FIG. 2 is a waveform diagram.

FIG. 3 is a block diagram showing a configuration of a driving circuit of a self-excited RCC according to the related art.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Main switch element 2, 3 First and second transistor 11 Transformer 12 Primary coil 13 Drive coil 17 Secondary coil 8, 15, 23, 28, 35 Capacitor 14, 20, 24, 30 Diode 26, 31 First And the second operational amplifier 36 DC power supply

Claims (1)

[Claims] A drive coil connected in parallel between a gate and a source of a main switch element constituting a self-excited RCC;
A first transistor for connecting a collector terminal and an emitter terminal to both ends of the first transistor, connecting a base terminal to a connection point of the voltage dividing resistors (6) and (7), and controlling on / off of a main switch element; A base connected to a connection point between two voltage-dividing resistors (21) and (22) in a series circuit including a diode (20) and two voltage-dividing resistors (21) and (22) connected in parallel to both ends of (13). Terminal, an emitter terminal connected to the ground side of the drive coil (13), and a capacitor (2) connected in parallel between the base terminal and the emitter terminal.
A non-inverting input terminal connected to a collector terminal of the second transistor and connected to a DC power supply (36) via a resistor (32), and a resistor (34). Drive coil (1
3) a second operational amplifier having an inverting input terminal connected to the ground side and connected to a DC power supply (36) via a resistor (33); and a capacitor (28) connected to the ground side of the drive coil (13).
And an inverting input terminal connected to the output terminal of the second operational amplifier via a diode (30) and a non-inverting input terminal connected to the ground side of the drive coil (13) via a resistor (29). Terminal and diode (24)
Is connected to the voltage-dividing resistor (6) provided at the base terminal of the first transistor through the resistors (25) and (2).
And 6) a multivibrator comprising a first operational amplifier having an inverting input terminal and an output terminal connected to the non-inverting input terminal via the multivibrator. Power drive circuit.