JPH10150765A - Switching regulator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize reduction in size and saving in cost. SOLUTION: The emitter-collector of a first transistor 11, a coil 12 and a first diode 5 are connected sequentially between an input terminal 3 and an output terminal 6. The connector of the first transistor 11 is grounded through a second diode 14 and the joint of the coil 12 and the first diode 5 is connected with the collector of an emitter earthed second transistor 13. The first diode 5 is earthed, on the output terminal side thereof, through a capacitor 7 and also connected with the voltage monitor terminal 4c of a PWM controller 4. The first and second transistors 11, 13 have bases connected, respectively, with the first and second control terminals 4a, 4b of the PWM controller 4. The PWM controller 4 controls the conduction angle of the first transistor 11 to sustain the voltage at the output terminal at a constant level and turns the second transistor 13 off for a predetermined time during off interval of the first transistor 11 thus charging the capacitor 7 with the electromagnetic energy of the coil 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a switching regulator, and more particularly to miniaturization and economy.

[0002]

2. Description of the Related Art A conventional switching regulator is shown in FIG.
As shown in FIG.
Is connected to one end of the primary coil and the other end is connected to the input terminal 3.
Connected to. The base of the transistor 1 is connected to the control terminal 4a of the PWM controller 4. One end of a secondary coil of the transformer 2 is grounded, and the other end is connected to an output terminal 6 through a diode 5. The cathode of the diode 5 is grounded through the capacitor 7.

A PWM controller 4 compares an output voltage Vout with a set voltage Vref, and controls a base current / voltage time width (flow angle) during which the transistor 1 is turned on so that the difference becomes zero. Usually, the switching of the transistor 1 is performed at a frequency of 20 KHz or more. FIG. 5B shows the output voltage V1 of the PWM controller 4 and the output voltage V2 of the transformer T. When the input voltage Vin = 6 to 14 V, the output voltage Vout ≒ 14 V and the output current IL ≒ 0.1 A are supplied to the load resistor 8. A commercially available PWM controller 4 can be used.

[0004]

Recently, there has been a strong demand for cost reduction and miniaturization of switching regulators. The present invention has been made to meet this demand.

[0005]

According to a switching regulator of the present invention, an emitter-collector, a coil, and a first diode of a first transistor are sequentially connected between an input terminal and an output terminal. ,
The connection point between the coil and the first diode is connected to the collector of the grounded second transistor at the emitter, the output terminal side of the first diode is grounded via the capacitor, and PWM Connected to the voltage monitoring terminal of the controller.

The bases of the first and second transistors are PWM.
The PWM controller is connected to the first and second control terminals of the controller, respectively. The PWM controller controls the flow angle of the first transistor so that the voltage of the output terminal becomes constant. The two transistors are turned off for a predetermined time to charge the capacitor with the electromagnetic energy of the coil.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The transformer 2 occupies a large proportion with respect to the cost structure and external dimensions of a conventional switching regulator. In view of this, the present invention realizes a switching regulator having a new circuit configuration that can be constituted by a relatively small and inexpensive coil 12, a PWM controller 4 for two channels and the like without using the transformer 2 as shown in FIG. In FIG. 1, the same reference numerals are given to portions corresponding to those in FIG.

The first transistor 11 has an emitter connected to the input terminal 3 and a base connected to the first terminal of the PWM controller 4.
Is connected to the control terminal 4a. The collector is connected to the anode of the first diode 5 through the coil 12. First
The anode of the diode 5 is connected to the collector of the second transistor 13 whose emitter is grounded, and the base of the second transistor 13 is connected to the second control terminal 4b of the PWM controller 4. The collector of the first transistor 11 is connected to the cathode of the second diode 14 whose anode is grounded.

FIGS. 2 to 4 show the experimental results of a model designed so that the output voltage V ≒ 14 V when the input voltage Vin = 6 to 20 V. FIGS. 2, 3, and 4 show A, B, and B of FIG. 1 when the input voltage Vin is 6 V, 14 V, and 20 V, respectively.
The waveforms of the voltages Vb, Vb ', Vc, and Vc' measured at points C and D are shown. The PWM controller 4 outputs the output voltage V
out is compared with the internal reference voltage Vref, and the time width (flow angle) of the base current / voltage during which the first transistor 11 is turned on is controlled so that the difference becomes zero. Figures 2-4
As can be seen, the input voltage Vin is 6V, 14V, 20V
, The time width of the negative voltage (FIG. A) supplied to the base for controlling the transistor 11 to be turned on is gradually narrowed, and the energy supplied to the power supply circuit is adjusted, whereby the output voltage becomes substantially constant. Will be retained.

(1) Period in which the first transistor 11 is on (T1) During the period in which the first transistor 11 is on, the base voltage (FIG. B) supplied to the second transistor 13 is at a high level, and 13 is controlled to be on. Therefore, the voltage Vc 'at the point D is clamped to approximately 0V.
A current flows from the input power supply to the path of the first transistor 11-the coil 12-the second transistor 13, and electromagnetic energy is accumulated in the coil 12. During this period, the charge of the capacitor 8 charged in the previous cycle is supplied to the load resistor 8.

(2) The period when the first transistor 11 is off During the period when the first transistor 11 is off, the base voltage is set to the H level. (2-1) Period in which the second transistor 13 is on (T2) The base voltage of the second transistor 13 is set to the H level,
During the period in which it is kept on, Vc 'at point D is approximately 0.
V clamped. The coil 12 retains the electromagnetic energy accumulated during the period (1). The first and second diodes 5, 14 are both turned off. The charge of the capacitor 7 is discharged to the load resistor 8.

(2-2) Period T3 in which the second transistor 13 is off The base voltage of the second transistor 13 is set to a low level,
When turned off, the electromagnetic energy accumulated in the coil 12 causes a current to flow through the path of the diode 14, the coil 12, the diode 5, and the capacitor 7, and the capacitor 7 is charged. The load resistor 8 includes a capacitor 7 and a coil 1
2, a current is supplied.

(2-3) Period in which the second transistor 13 is on (T4) When the second transistor 13 is controlled to be turned on again, Vc 'at the point D is clamped again to approximately 0V. 1st, 2nd
The diodes 5 and 14 are turned off. The charge of the capacitor 7 is discharged to the load resistor 8.

[0014]

According to the present invention, a relatively small and inexpensive coil 12, transistor, diode and the like are used without using a large and expensive transformer as in the prior art.
A smaller and less expensive switching regulator than before can be realized.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention.

FIG. 2 is a waveform diagram of a main part of FIG. 1 when an input voltage is 6V and an output voltage is 14V.

FIG. 3 is a waveform diagram of a main part of FIG. 1 when an input voltage is 14 V and an output voltage is 14 V;

FIG. 4 is a waveform diagram of a main part of FIG. 1 when an input voltage is set to 20V and an output voltage is set to 14V.

5A is a circuit diagram of a conventional switching regulator, and FIG. 5B is a waveform diagram of a main part of A.

Claims (1)

[Claims] 1. An emitter-collector, a coil, and a first diode of a first transistor are sequentially connected between an input terminal and an output terminal, and a collector of the first transistor is grounded through a second diode. The connection point of the first diode is connected to the collector of the second transistor whose emitter is grounded, and the output terminal side of the first diode is grounded via a capacitor and connected to the voltage monitoring terminal of the PWM controller. The bases of the first and second transistors are respectively connected to the first and second control terminals of the PWM controller, and the PWM controller adjusts the flow angle of the first transistor so that the voltage of the output terminal becomes constant. Control, and in the off period of the first transistor, the second transistor is turned off for a predetermined time. And your switching regulator, characterized in that for charging the capacitor with electromagnetic energy of the coil.