JPH04368463A - Power source - Google Patents

Abstract

PURPOSE:To maintain supply of energy to a series resonance circuit with a high efficiency by interposing switch means between alternate switches of a full bridge and a DC input. CONSTITUTION:A resonance circuit has a series resonance of an output transformer(OT) 2 and a capacitor (CD) C4. Driving of the resonance circuit is executed by a full bridge having transistors(Tr) 4-7. The operation of alternate switches is executed by a circuit of an oscillator 12, a driving circuit 13 and a driving transformer 11. Currents during the operation of a diode D1, flow in a half cycle of a circuit of a DO D1, the Tr 4, the CD C4, the OT 2, the Tr 7 and the DO D1, and a half cycle of a circuit of the DO D1, the Tr 5, the OT 2, the CD C4, the Tr 6 and the DO D1. In the meantime, the charging energy of the CD C4 is converted to electromagnetic energy of the OT 2 to partly become an output energy. An error signal of an output Vo controls the output Vo by a feedback loop of an error detector 14, a photocoupler 15, a control circuit 16, a pulse transformer 10 and a Tr 3.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply device that obtains a stabilized direct current from a commercial power source, and more particularly to a circuit configuration of a power supply device using resonance type switching operation.

0002

2. Description of the Related Art FIG. 3 shows an embodiment of a resonant power supply circuit according to the prior art. Input 1 represents a DC input terminal obtained by rectifying and smoothing commercial power, and V1N represents its voltage. C0 is a smoothing capacitor, and C1 and C2 are capacitors with the same capacity that divide the voltage V1N approximately in half. L and C3 are a coil and a capacitor that resonate in parallel. C4 is capacitor C1
This capacitor has a smaller capacitance than C2 and resonates in series with the leakage or excitation inductance of the output transformer 2.

[0003] Capacitor C3, coil L, capacitor C
4. FIG. 4 shows the overall impedance characteristics of the transformer 2. f1 and f3 represent series resonant frequencies, and f2 represents parallel resonant frequencies.

The operating frequency range f of the prior art in FIG.
2<f<f3, and the frequency is from 30 KHz to several MHz.

Transistors Tr1 and Tr2 constitute a half-bridge drive and are alternately conductive. A rectifier 3 rectifies the induced voltage in the secondary winding of the transformer 2. The output voltage Vo is obtained by smoothing with a smoothing capacitor C5. 4 represents an output terminal.

The error detector 5 detects an error between the output voltage Vo and a reference value, and provides an error signal to a photocoupler 6 that separates the primary side and the secondary side. The VCO 7 is a voltage controlled oscillator whose input voltage and oscillation frequency correspond to each other. For example, when the output voltage Vo is higher than the reference value, the output of the photocoupler is reduced and the oscillation frequency is lowered. The drive circuit 8 drives the transistors Tr1 and Tr2 at a low frequency. In the resonant circuit of FIG. 3, the impedance increases, so the current decreases. As a result, the energy transferred to the output of the output transformer 2 decreases, and the output Vo decreases. In this way, the output Vo is stabilized.

[0007] V1N is 100 to 140 volts when the commercial power supply is 100 volts, and 260 to 140 volts when the commercial power supply is 220 volts.
It is 360 volts. The output Vo is normally about 5 to 50 volts.

[0008] The features of the above conventional technology will be summarized.

1. Since the transistors Tr1 and Tr2 switch with zero current, switching loss is small.

2. The output Vo is stabilized by modulating the frequency of VcO7 and utilizing the frequency characteristics of the raw impedance.

[0011] Overall, high efficiency can be obtained with an essential P loss of only control power. The above is the power supply device according to the prior art.

0012

Problems to be Solved by the Invention Originally, switching power supply devices are designed to be faster and have smaller components to improve efficiency and reduce weight. In addition, the resonance type is used to reduce switching loss by setting the operating point of the switching element to zero voltage or current, and to suppress spikes and relegging caused by sudden current changes, thereby reducing electromagnetic radiation. .

However, although the conventional techniques described above have achieved the above object, they have the following problems.

1. The operating frequency f in FIG. 3 is f2<f<f
3, and if, for example, f1<f<f2, the control characteristics will be reversed and a runaway will occur. Therefore, an additional circuit for monitoring the resonance condition is required and is expensive.

2. The capacitors and coils that form the resonant circuit require sufficient high-frequency characteristics and current capacity, but the components are four capacitors, C1, C2, C3, and C4, and two inductances, output transformer 2 and coil L. Too many wiring problems and high costs.

In order to avoid runaway in 3.1, the frequency variable range of Vco7 is narrowed and the impedance of the resonant circuit may not rise sufficiently at light loads, causing the output Vo to rise, so a dummy load is required. . This impairs the originally high efficiency.

SUMMARY OF THE INVENTION The present invention is intended to solve these problems, and its purpose is to reduce the number of components of a resonant circuit to provide a low cost, safe control characteristic, and highly efficient power supply device. Our goal is to provide the following.

[0018]

[Means for Solving the Problems] The power supply device of the present invention provides a power supply device that obtains a stabilized DC output by performing switching control on a DC input obtained by rectifying a commercial power source, and includes a switch means for switching the DC input. , an alternating switch means that receives electric power from the switch means, a resonant circuit including an output transformer excited by the alternating switch means, an output means that rectifies and outputs the induced voltage of the secondary winding of the output transformer, and the output transformer. The alternating switch means includes a feedback means for returning an error signal of the means to the switch means, and the alternating switch means forms a power supply device that operates at a predetermined cycle, thereby eliminating runaway, achieving high efficiency, low cost, and reducing electromagnetic radiation. It has the following.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a diagram showing a specific circuit configuration in an embodiment of the present invention. The same numbers or signals as in FIG. 3 have the same meanings.

The resonant circuit shown in FIG. 1 is represented by series resonance between the output transformer 2 and the capacitor C4. The resonant circuit is driven by forming a full bridge structure in which transistors Tr4 and Tr7 and transistors Tr5 and Tr6 are alternately conductive.

[0021] This switching frequency is set lower than the series resonant frequency to reduce switching loss. DC input V
A transistor Tr3 is provided between the 1N transistor and a transistor with a fool bridge configuration (hereinafter referred to as an alternating switch) to control power supply.

The operation of the alternating switch is performed by the oscillator 12 -> the drive circuit -> the drive transformer 11, and has a substantially constant cycle. This operating frequency is selected from the aforementioned 30 KHz to several MHz.

The error signal of the output Vo is transmitted from the error detector 14→photocoupler 15→control circuit 16→pulse transformer 10→
The output Vo is controlled by the feedback loop of the transistor Tr3.

The operation timing and operation waveforms will be explained with reference to FIG. 2(a) and 2(b) show the operating timing of the alternating switch, and FIG. 2(c) shows the operating timing of the transistor Tr3, which is also turned on and off near zero current to reduce switching loss. Therefore, the drive circuit 13 and the control circuit are associated in FIG.

The ON/OFF state of the transistor Tr3 is approximately 100% ON at full load, and the ON decoty is reduced at light load. Therefore, since the power supply to the resonant circuit can be controlled, runaway will not occur.

Control can be achieved by modulating the operating frequency of the alternating switch, but in the case of no load or light load, the frequency becomes audible, causing the problem that the output transformer 2 becomes a sound source.

Therefore, the transistor Tr3 is provided to alternately operate the mechanical stress of the output transformer 2 at substantially the same period at frequencies other than the audio frequency. transistor T
r3 does not become a sound source even at low frequencies. If the system is implemented using only alternating switches, efficiency will decrease because a dummy load is added to avoid the above problem and the system does not operate at an audible frequency.

FIG. 2(d) shows the voltage waveform of capacitor C4 in the resonant circuit, and FIG. 2(e) shows the current waveform.

(f) shows the rectified waveform of the induced voltage in the secondary winding of the output transformer 2 and the output Vo using a dotted line. This output Vo
Current flows through the secondary winding at the point where the current exceeds . This current changes the magnetic flux of the output transformer 2 and affects the current and voltage waveforms of the resonant circuit, but they are shown as sine waves.

Incidentally, in the present invention, although the number of resonant circuits is reduced, the number of transistors serving as switching elements is increased by three compared to FIG. However, compared to the aforementioned capacitors and coils, which have strict characteristics, they are not only cheaper, but also operate with less switching loss, which facilitates thermal design and makes them more compact. In addition, since a large current flows in reality, both the capacitor and the coil generate heat, and it is necessary to pay attention to thermal design, so it is better to replace them with semiconductor elements.

The diode D1 in FIG. 1 is connected to the transistor T
This is because a resonance current flows when r3 is OFF.

Although not shown, the alternating switch transistors Tr4, Tr5, Tr6, and Tr7 are provided with protective diodes.

The current when the diode D1 is operating is as follows: diode D1 → Tr4 → capacitor C4 → output transformer 2 →
The cycle is a half cycle of Tr7→D1 and a half cycle of D1→Tr5→output transformer 2→capacitor C4→Tr6→D1. During this time, the charging energy of the capacitor C4 is converted into electromagnetic energy of the output transformer 2, and part of it becomes output energy, and the rest is due to loop resistance loss, and the capacitor C4 is charged in the opposite direction and repeats this cycle while attenuating. Although the resonant circuit may be modified, it is configured so that no direct current flows.

[0034]

[Effects of the Invention] As described above, according to the configuration of the present invention,
By using a Fool-bridge alternating switch to supply energy to the series resonant circuit, and by interposing a switching means between the alternating switch and the DC input, high efficiency is maintained, the characteristics of the resonant type are utilized, and the cost is reduced. The effect is extremely large.

[Brief explanation of the drawing]

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

FIG. 2 is a diagram showing the operation timing and operating voltage and current waveforms of each part in FIG. 1;

FIG. 3 is a diagram showing an embodiment according to the prior art.

FIG. 4 is a diagram showing the overall impedance characteristics of the resonant circuit used in FIG. 3;

Claims (1)

[Claims] 1. A power supply device that obtains a stabilized DC output by controlling switching of a DC input obtained by rectifying a commercial power supply, comprising a switch means for switching the DC input, and an alternating switch means for receiving power from the switch means. a resonant circuit including an output transformer excited by the alternating switch means, an output means for rectifying and outputting the induced voltage of the secondary winding of the output transformer, and an error signal of the output means being fed back to the switch means. A power supply device comprising a feedback means, wherein the alternating switch means operates at a predetermined cycle.