JPS5936148Y2 - switching regulator - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a starting circuit for a switching regulator.

Conventionally, a switching regulator as shown in FIG. 1 has been used in television receivers in order to stabilize the power supply voltage.

In Figure 1: AClooV supplied to terminals 1 and 2
The AC voltage is rectified and smoothed by the power supply circuit 3 to become a DC voltage V1.
becomes.

This DC voltage V1 is supplied via capacitors C1 and C2 to a switching circuit 4 composed of a pair of transistors Q1 and Q2, and is also supplied to a starting oscillation circuit 5 via a resistor R1 and a capacitor c3.

This oscillation circuit 5 includes a transistor Q3, a capacitor C4
s C5, resistor R21R3, diode D1, and oscillation transformer T1.

A transistor Q4 is connected to this oscillation circuit 5 for stopping the oscillation operation.

The secondary output of the oscillation transformer TI is rectified and smoothed by a diode D2 and a capacitor C6, and then supplied to a PWM circuit (pulse width modulation circuit) 13 as a power supply voltage element B.

On the other hand, the output transformer T2 has a coil 6.1 for stopping oscillation.
A next output coil 7, a secondary output coil 8, a secondary drive coil 9, 10, and a primary drive coil 11.12 are provided.

The coil 6 is connected to the base of the transistor Q4 via a diode D3 and a resistor R4.

The coil 7 is connected between the connection point between the capacitors C1 and C2 and the connection point between the transistors Ql and Q2.

The coils 9.10 are connected to the bases of transistors Q1-Q2, respectively.

Coils 11 and 12 are connected to two output terminals of PWM circuit 13, respectively.

The AC voltage obtained at the coil 8 is rectified and smoothed by a rectifier circuit 14 to become a DC output voltage V2.

This output voltage V2 is supplied to a predetermined load 15 in the television receiver, and is also supplied as a power supply voltage element B to the PWM circuit 13 via a diode D4.

The output voltage V2 is further divided by a variable resistor R5 and applied to a voltage comparison circuit 16, where it is compared with a reference voltage V.

The voltage that is the difference between this voltage v2 and VsO is the control voltage ■.

By applying this to the PWM circuit 13, the duty ratio of the output pulse is controlled.

Next, the operation of the above configuration will be explained.

When the power is turned on, the oscillation circuit 5 operates with the voltage v1 obtained from the power supply circuit 3.

This oscillation output is applied to the PWM circuit 13 after being rectified and smoothed by a diode D2 and a capacitor C6 via a transformer T1.

As a result, the PWM circuit 13 starts operating at a predetermined frequency, and output pulses having mutually opposite phases are obtained in the coils 11 and 12.

This pulse is applied to the coil 9.10, which initially causes, for example, the transistor Q1 to conduct, which causes a current 11 to flow in the coil 7.

Next, the transistor Q2 becomes conductive, and a current I2 flows through the coil 7 in the opposite direction to the current (1).

A voltage is induced in the coil 6 by this current (1) or (2), and this voltage is applied to the base of the transistor Q4 through the diode D3 and the resistor R4, thereby making the transistor Q4 conductive.

As a result, the operation of the oscillation circuit 5 is stopped.

Therefore, the power supply voltage applied from this oscillation circuit 5 to the PWM circuit 13 is cut off.

On the other hand, an alternating current voltage is induced in the coil 8 by the current 11sI2, and this alternating voltage is turned into an output voltage ■2 by the rectifier circuit 14.

By applying this output voltage 2 as a power supply voltage to the PWM circuit 13 through the diode D4, this PWM
M circuit 13 continues to operate.

Based on the output of the PWM circuit 13, the transistors Ql-Q2 are alternately switched, so that
Output voltage V2 is obtained.

This output voltage V2 is transferred from the variable resistor R5 to the voltage comparator circuit 16.
is added to and compared with reference voltage ■3.

Therefore, when the output voltage (■2) fluctuates, the control voltage (■) changes accordingly.

changes, and the duty ratio of the pulses applied to the coils 11, 12 is controlled accordingly, thereby making it possible to control the output voltage V2 to be constant.

In the switching regulator described above, generally, a circuit connected to the primary side of the output transformer T2, that is, a circuit 4.3 of coil 7, 9, 10, etc., and a circuit that is connected in a quadratic manner, that is, coil 8. .11゜12 side circuit 13,1
4. The 15, 16 and 18 degrees 19, the transistor Q5, etc. are provided in separate chassis, and these two chassis are insulated via the output transformer T2.

As a result, the primary chassis 4 becomes a so-called hot chassis with a live part, and the secondary chassis becomes a so-called cold chassis.

Therefore, insulation of the antenna terminal, earphone jack connection terminal, VTR video signal output terminal, audio multiplex terminal, etc. provided on the secondary side chassis can be made unnecessary.

When starting up the una switching regulator like this,
As described above, the oscillation circuit 5 is caused to oscillate, and the power supply voltage for the PWM circuit 13 is obtained based on this oscillation output.

This oscillation circuit 5 is provided in the primary side chassis, and
It is insulated from the PWM circuit 13 provided on the next chassis via an oscillation transformer T1.

Therefore, the starting circuit 17 required a complicated circuit configuration as shown by the part surrounded by the dotted line in FIG.

Therefore, it is possible to omit this startup circuit 17 and directly apply the voltage v1 obtained from the power supply circuit 3 to the PWM circuit 13 when the power is turned on. Therefore, this method cannot be used because it is no longer possible to insulate the circuit.

The present invention is intended to solve the above-mentioned problems, and an embodiment in which the present invention is applied to a television reception system that allows remote control will be described below with reference to FIG. 2.

In FIG. 2, the same parts as in FIG. 1 are given the same reference numerals.

In FIG. 2, the receiver has a power supply circuit 18 for the remote control.
is provided separately from the main power supply circuit 3.

This power supply circuit 18 includes a transformer T3 and a diode D6.
* It is composed of D7 and a capacitor C3, and its input end is connected to terminal 1.2 to which an AC voltage of 100V is applied.

The power supply circuit 18 always outputs a DC voltage (3) of, for example, 12V, and this DC voltage (3) is applied to the remote control circuit 19 and the emitter of the transistor Q5.

The remote control circuit 19 is conventionally known, and is operated by various remote control signals applied from the outside to perform operations such as opening and closing the main power switch of the receiver and changing channels.

The collector of the transistor Q5 is connected to the +B power supply terminal of the PWM circuit 13, and the base resistor R65R7 and the capacitor C
7 to the output terminal 20 of the output voltage V2.

The output terminal 20 is also connected to the 10B power supply terminal of the PWM circuit 13 via a diode D5.

Next, the operation of the above configuration will be explained.

When the main power is not applied to the receiver, the base of the transistor Q5 is at ground potential, and therefore the voltage V3 of the power supply circuit 18 is applied to the PWM circuit 13 through the emitter and collector of the transistor Q5.

This causes the PWM circuit 13 to operate.

In this state, when the power is turned on by remote control operation or manually, the coil 11.1 is transferred from the PWM circuit 13 to the coil 11.1.
Transistor QryQ2 immediately starts a switching operation based on the pulse outputted to QryQ2.

As a result of this switching, the above-mentioned operation is performed.
An output voltage V2 is obtained at the output terminal 20.

By applying this voltage V2 to the base of transistor Q5, this transistor Q5 is cut off,
As a result, the voltage v3 applied to the PWM circuit 13
is blocked.

At the same time, the output voltage V2 is changed to PW through the diode D5.
Since it is added to the M circuit 13, the stiffness PWM circuit 13 is continuously operated.

According to the above, the power supply circuit 18 for remote control
By effectively utilizing the voltage ■3, the conventional
The switching regulator can be started by omitting the starting circuit 17 in the figure and providing a simple switch circuit using the transistor Q5.

Although the PWM circuit 13 operates even when the switch regulator is not operating, the power consumption is extremely small since it operates under almost no load conditions.

Further, the terminal 1.2 and the output end 20 can be insulated via a transformer T3.

As described above, the present invention provides the first
The first DC voltage V is applied to the side (coil 8, 11, 12 side)
2, and the first DC voltage ■
2 is supplied to the power supply terminal of the pulse width modulation circuit 13, and a comparison circuit that compares the first DC voltage V2 and the reference voltage 3 and controls the output duty ratio of the pulse width modulation circuit 13 using the comparison output. 16, a second power supply circuit 18 for obtaining a second DC voltage v3, and the first DC voltage V2 for supplying the second DC voltage v3 to the power supply terminal of the pulse width modulation circuit 13. The first switch circuit Q
5, and a third power supply circuit 3 that obtains a third DC voltage from the AC power supply voltage on the second side (coil?, 9.10 side) of the first transformer T2, and The pulse width modulation circuit 13 for switching the DC voltage is also connected to the second switch circuit Q1, which is controlled by pulses supplied via the first transformer T2. Q2 is provided, and the AC power supply voltage is supplied to the second power supply circuit 18 via the second transformer T3, and the second switch circuit Q2 is provided.
The switching output of l-Q2 is connected to the first transformer T2.
When the AC power supply voltage is applied, the first switch circuit Q5 is made conductive and the second DC voltage V3 is supplied to the first power supply circuit 14 through the pulse width modulation. is supplied to the power supply terminal of the circuit 13, and when the first DC voltage V2 is obtained, the first switch circuit Q5 is rendered non-conductive, and the first DC voltage 2 is applied to the pulse width modulation circuit 13. The present invention relates to a switching regulator characterized in that the power is supplied to the power terminal of the switching regulator.

Therefore, according to the present invention, the power supply circuit 3 is installed in the hot side chassis.
and switching transistors Ql-Q2, and other various circuits 13, 14, 18, . . . are arranged on the cold side chassis.
16 mag. can be arranged.

By arranging the various channels 13, 14, 18, 16, etc. on the cold side chassis, the second power supply circuit 18 can be effectively used as a remote control power supply circuit that has been conventionally provided on the cold chassis. can be used.

Further, both chassis can be completely insulated, and startup can be performed simply by adding a circuit with a simple configuration, without providing a complicated startup circuit as in the conventional case.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram of a conventional switching regulator, and FIG. 2 is a circuit diagram showing an embodiment of the present invention. In addition, in the symbols used in the drawings, 4......Switching circuit,...Voltage comparison circuit, 1 20...Output end, T2 13...PWM Circuit, 16 8...Remote control power supply circuit,... Output transformer.

Claims (1)

[Scope of utility model registration request] A first to obtain a first DC voltage on the first side of the first transformer.
a power supply circuit, a pulse width modulation circuit whose power supply terminal is supplied with the first DC voltage, and a pulse width modulation circuit that compares the first DC voltage with a reference voltage and uses the comparison output to determine the output duty ratio of the pulse width modulation circuit. a second power supply circuit for obtaining a second DC voltage; and a first power supply circuit for supplying the second DC voltage to the power supply terminal of the pulse width modulation circuit.
a first switch circuit controlled by a DC voltage of
from the AC power supply voltage to the second side of the first transformer.
a third power supply circuit that obtains a DC voltage; and a second switch circuit that is controlled by pulses supplied via the first transformer from the pulse width modulation circuit for switching the third DC voltage. and supplying the AC power supply voltage to the second power supply circuit via the second transformer, and supplying the switching output of the second switch circuit to the first power supply circuit via the first transformer. When the AC power supply voltage is applied, the first switch circuit is made conductive and the second DC voltage is supplied to the power supply terminal of the pulse width modulation circuit. A switching regulator characterized in that when a DC voltage is obtained, the first switch circuit is rendered non-conductive and the first DC voltage is supplied to a power supply terminal of the pulse width modulation circuit.