JPS60170466A - Switching regulator - Google Patents

Abstract

PURPOSE:To obtain a stable output irrespective of the variation in the voltage of a power source by altering the duty ratio of a pulse signal for turning ON and OFF the primary circuit of a converter. CONSTITUTION:A commercial frequency power source 11 is rectified by a diode bridge 12, a choke coil 13 and a smoothing coil 14, and applied to a series circuit of the primary winding 15a of a pulse transformer 15 and a transistor 16. The power source 11 is stepped down by a transformer 23, and applied through a rectifier 24 and a constant-voltage circuit 25 to an oscillator 26. The output pulse of the oscillator 26 is applied through a pulse transformer 18 to the switching transistor 16. The duty ratio of the output pulse of the oscillator 26 is altered by a variable resistor 16c, and the prescribed voltage can be obtained by the regulation irrespective of the voltage of the power source 11.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a switching regulator used in a power supply circuit of an electric appliance.

[Prior art]

FIG. 1 is a schematic circuit diagram of a 40 (four burners) electromagnetic cooker.

The commercial frequency power supply 1 becomes a direct current through a power supply, a power supply 2, a choke coil 3, a normal temperature capacitor 4, etc., and the voltage between the terminals VDC and GND obtained by this rectifier circuit is converted to a single endoscope including a heating coil 50. Push-pull type inverter circuits 5, 5, 5゜5 are applied to terminals V DC and GND of the same sign, respectively.The inverter circuit 5 is equipped with a series resonant circuit consisting of a heating coil 50 and a resonant capacitor 51 points, and this series resonant circuit is It is connected in parallel with the switching transistor 52 and in anti-parallel with the flywheel diode 53. Switching 1 - transistor 52
has its collector connected to the terminal VDC, and its emitter connected to the collector of another switching i transistor 54. The emitter of transistor 54 is terminal G
ND, and a diode 55 is connected in antiparallel to this transistor 54.

Then, a pulse signal is applied from the control circuit 7L72, 73 or 74 to each of the transistors 1 to 54 to turn them on. Then, a current flows in the direction of the arrow in the heating coil 50, and the capacitor 51 is charged by this current.

1 to transistor 52 after turning off the transistor 54
In order to turn on, the terminals VB+, VIE+ (or νBz, VB
2, VB3.

When a pulse signal is applied to VB (or νL, VEI) from the switching regulator 6, the charge in the capacitor 51 is discharged, and a current flows in the coil 50 and the transistor 52 in the opposite direction to the arrow.

Control circuits 71 to 711' VIl+ to Vl+4, VN+ to VN4 and VL of switching regulator 6
A predetermined DC voltage is applied to each of the three terminals 1 to V L 4.

1] By alternately turning on the transistors 52 and 54 as described in 2), a high frequency current flows through the coil 5a,
It is possible to heat a pot (not shown) placed on this coil, as well as food inside the pot.

In this way, when the switching regulator is used as a power source for the inverter circuit 5, control circuit 71, etc., a low frequency transformer and a pulse transformer are required for each heating coil circuit.1] The structure is simpler than the conventional circuit. It can be made lighter and lighter.

However, in the switching regulator, it is necessary to change the turns ratio of the internal pulse transformer depending on the type of power supply voltage (IooV, 120V, 220V, 240V, etc.). In addition, in order to apply the required voltage to the inverter circuit 5 without changing the turn ratio of the pulse transformer, it is necessary to change the duty ratio of the oscillation frequency of the drive system, but if this is done, the voltage at the terminal VB.

The timing of the pulse signal output between ~VB and the terminals VE and ~VEI also changes, making it impossible to operate the in-hark circuit 5 as desired.

〔the purpose〕

The present invention has been made to solve these problems, and an object of the present invention is to provide a switching regulator that can provide a stable output regardless of changes in power supply voltage.

[Structure of the invention]

A switching regulator according to the present invention is a switching regulator that receives an AC power source as an input and outputs a pulse signal and a constant DC voltage. a converter for converting into a DC voltage, and one of the converters.
It is characterized in that it is equipped with an oscillator with a variable duty ratio that emits a pulse signal that controls on/off of the next circuit, and that by adjusting the duty ratio, the output can be stabilized regardless of the voltage of the AC power source.

〔Example〕

The present invention will be explained in detail below based on FIG. 2 showing an embodiment thereof.

The commercial frequency power supply 11 is a diode bridge. The DC current is rectified by a choke coil 13 and a smoothing coil 14, and is applied to a series circuit of a primary winding 15a of a pulse transformer 15 and a transistor 16. A diode 17 is connected in antiparallel to the primary winding 15a.

Further, a pulse signal for controlling on/off of the transistor 16 is applied from the secondary winding 18b of the pulse transformer 18 between the base and the emitter of the transistor 16. The secondary winding 15b and the tertiary winding 15c of the pulse transformer 15 have one end connected in common, and the anodes of diodes 19 and 20 are connected to the other end, and there is a connection between each cathode and the above one end. A rectifier circuit is constructed in which capacitors 2] and 22 are connected to the cathodes to obtain potentials of +V and +Vcc.

That is, pulse transformer 15. Transistor 16. A diode 19, 20, a capacitor 21, 22, etc. constitute an on/off type single-ended forward converter.

The commercial frequency power supply 11 is also stepped down by a transformer 23, rectified by a rectifier circuit 24, and connected to a Zener diode '25a.
is applied to a constant voltage circuit 25 using a constant voltage circuit 25, and the voltage →-Vc obtained thereby is applied to an oscillator 26.

The oscillator 26 is a timer IC (type 555) 26a, 26
IC26b are connected in series so that the IC26a at the front stage performs astable operation and the IC26b at the rear stage performs monostable operation.
The output of a is given to IC26b and the output terminal of IC26h (
3) to obtain a pulse signal having a time width and duty ratio determined by the constants of the external circuits of both ICs. The duty ratio is made variable by adjusting the variable resistor 26c between the terminal 7 of the IC 26b and the line of potential 1 Vc.

The series circuit of the primary winding 18a of the pulse transformer 18 and the transistor 27 is configured such that →-Vc is applied, and the pulse signal is applied to the transistor 27 to connect the secondary winding of the pulse transformer 18. Inducing a pulsed current in the wire -l
, this pulse signal turns on the transistor 16.

Turn it off.

The terminal voltage of the capacitor 21, 10 V, is applied to the intermediate terminal of the primary winding 28a of the output pulse transformer 28. The collectors of transistors 29 and 30 whose respective emitters are connected together are connected to both ends of this primary winding 28a, and the emitters are connected to capacitors 2 and 2.
It is connected to the common side terminal of 2.

31 is fc for switching regulator control
(for example, NEC μPC1042), and to drive it, both terminals of the capacitor 22 are connected to +■c
There is nothing like applying c. The output of this IC 31 controls ON/OFF of the 1-transistors 29 and 30 to drive the output pulse transformer 28.

The secondary winding 28b of the pulse transformer 28 has terminals VB and VE to be connected to the terminals VB+, VB+, etc. of the inverter circuit 5 shown in FIG. Also, the tertiary winding 28
Anode F of a diode 32 is connected to one end of C, and its can-1 is connected to terminal Vl+, and a capacitor 33 is connected between it and the intermediate terminal VN of the tertiary winding 28c.

The cathode of a diode 1''34 is connected to the other end of the tertiary winding 28c, and its anode is connected to the terminal VL, and a capacitor 35 is connected between it and the terminal νN to form two rectifier circuits. As a result, terminals VB and VH
In between, a pulse voltage having a time width and a duty ratio determined by the on/off state of the 1-transistors 29 and 30 is obtained, and the transistor 52 is driven by this. Also, the terminal Vll
, VN, VL, a constant voltage is obtained where VH is the highest (VN, NL and lower.Vll, VN.

VL is connected to the control circuit 7], 72□73.74 in FIG. 1, and its power supply voltage can be obtained by ii.

In a circuit with such a configuration, terminals VB, νE, and VH.

The potentials of VN and VL are determined by the terminal voltage of capacitor 2■ of 10 V, and the correct voltage is determined by the correct operation of IC31.
Alternatively, a duty ratio of 1 time width of the pulse signal can be obtained. Therefore, it is necessary to stabilize the potential of 10V applied to the pulse transformer 28 and the potential of 10Vcc applied to the IC 31, but in the circuit of the present invention, by adjusting the variable resistor 26c, it is possible to stabilize the voltage of the commercial frequency power supply 11 regardless of the voltage of the commercial frequency power supply 11. A predetermined +V and 10 VCC are obtained. That is, a single-ended circuit including a pulse transformer 15, a transistor 16, etc.
In a forward converter, the output voltage VD is Vo-(1/n) ・(D/I
D) ・Vin However, n is the winding ratio and is expressed as the duty ratio. Therefore, without changing the turns ratio n (Vi
In order to keep Vo constant regardless of n, it is sufficient to adjust the duty ratio, but in the circuit of the present invention, by adjusting the variable resistor 26c, the transistor 27, and therefore the transistor 6, can be turned on and off. Since the duty ratio is changed by iη, it is possible to keep ①o constant, that is, 10V and 10Vcc in this case.

For example, if the duty ratio is set as D=0.5 when the voltage of the commercial frequency power supply 11 is 100V,
When the voltage of the commercial frequency power supply 11 changes to 240V, adjust the variable resistor 2 so that D=0.294 according to the above formula.
6c All you have to do is shift the fc adjustment.

In the above-mentioned embodiment, the output pulse transformer 31 had a single endoscope 1~ push-pull type winding, so the IC 31 capable of generating a two-phase split output was used to drive it. When driving the output pulse I/lance in a forward manner, an oscillator combining a timer circuit and a gate circuit may be used.

〔effect〕

In the case of the switching regulator of the present invention as described above, even if the power supply voltage differs, the duty ratio of the pulse signal for turning on and off the converter primary circuit is changed, and in the embodiment, the variable resistor 16 is adjusted to 0, so that this can be handled. Therefore, there is no need to change the turn ratio of the pulse transformer, and even if the resistance value of the variable resistor is changed, the timing of turning on and off the 1-transistor 52 of the impark circuit 5 is not affected in any way. I don't know anything. As described above, according to the present invention, it is possible to realize a switching regulator that can extremely easily cope with changes in the power supply voltage.

[Brief explanation of drawings]

FIG. 1 is a schematic circuit diagram of a 40 electromagnetic cooker, and FIG. 2 is a schematic circuit diagram of a switching regulator of the present invention. 11... Commercial frequency power supply 15, 18. 28... Pulse transformer 16... Transistor 26... Oscillator 26c... Variable resistor patent Applicant: Sanyo Electric Co., Ltd. Agent Patent attorney: Noboru Kono 1 Prison 2 diagram

Claims (1)

[Claims] 1. In a Swiss converter that receives an AC power source as input and outputs a pulse signal and a constant DC voltage, the DC voltage obtained by rectifying the AC power source is converted into the DC voltage to be applied to the output pulse transformer. It is equipped with a converter converter and an oscillator with a variable duty ratio that emits a pulse signal that controls on/off of the primary circuit of the converter, and by adjusting the duty ratio, the output can be made regardless of the voltage of the AC power supply. Sui is characterized by the fact that it cannot be stabilized.
Nochinda regulator.