JPH07236271A - Resonance-type switching power supply - Google Patents

Abstract

PURPOSE:To omit a current detecting circuit and to achieve the cost reduction and the compact configuration by controlling the output current in an output circuit on the basis of the voltage which is detected in a resonant-voltage detecting circuit. CONSTITUTION:The voltage of an output terminal 6 is compared with a reference voltage source 4 and an error amplifier 3. The ON and OFF of switching elements Q1 and Q2 are controlled with a control circuit 2. Thus, the voltage of the output terminal is controlled at the constant value. A current detecting circuit is omitted. In place of the current detecting circuit, the voltage of a resonance capacitor C1 is detected with a line 8 as a voltage detecting circuit, and the detected voltage is sent into the control circuit 2. When the voltage of the output terminal 6 is controlled at the constant value, the rectified output voltages of the capacitor C1 and a primary winding rise up in proportion to a load current. Therefore, the current detection is achieved with a simple constitution wherein the voltage of the capacitor C1 is detected with the line 8, and the low cost and the compact configuration are achieved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resonance type switching power supply device which uses resonance between an inductance and a capacitor connected in series with the inductance.

[0002]

2. Description of the Related Art FIG. 1 shows a conventional resonance type switching power supply device. This switching power supply device includes a series circuit of transistors Q1 and Q2 as first and second switching elements connected between one end and the other end of a DC power supply 1, an output transformer T1, and an output transformer T1. A first resonance capacitor C1 connected in series to the primary winding N1; second and third capacitors C2 and C3 connected in parallel to the first and second transistors Q1 and Q2; And the first and second clamping diodes D1 and D connected in reverse parallel to the second and second transistors Q1 and Q2.
2, the control circuit 2 connected to the bases (control terminals) of the first and second transistors Q1 and Q2, the secondary windings N2a and N2b of the output transformer T1, and the secondary windings N2a and N2b.
It has a rectifying / smoothing circuit composed of diodes D3, D4 and a smoothing capacitor C4 connected to each other, an error amplifier 3, a reference voltage source 4, and a current detector 5.

The series circuit of the primary winding N1 and the capacitor C1 is connected in parallel with the second transistor element Q2. The transformer T1 is a leakage transformer, and the primary winding N1 and the secondary windings N2a and N2b are roughly coupled via a core 9. The secondary windings N2a and N2b are connected in a center tap type. A load (not shown) is connected to the output terminal 6 connected to the smoothing capacitor C4. One input terminal of the error amplifier 3 is connected to the output terminal 6, the other input terminal is connected to the reference voltage source 4, and the error output line 7 is connected to the control circuit 2. This error amplifier 3
Outputs a voltage corresponding to the difference between the output detection voltage and the reference voltage. The current detector 5 consisting of a current transformer is connected to the control circuit 2 by a line 8.

As shown in FIG. 2, the control circuit 2 includes a VCO (voltage controlled oscillator) 11, a waveform shaping circuit 12, a NOT circuit 13, a current detecting rectifying / smoothing circuit 14, and a comparator 15.
And an overcurrent detection reference voltage source 16 and an off control transistor 17.

The VCO 11 is connected to the output line 7 of the error amplifier 3 shown in FIG. 1, and the oscillation frequency becomes high when the detection voltage at the output terminal 6 is higher than the reference value, and becomes higher when the output detection voltage is lower than the reference value. Is configured to be low. The output of the VCO 11 is shaped into a square wave by the waveform shaping circuit 12 and sent to the base (control terminal) of the first transistor Q1 via the line 18, and also via the NOT circuit 13 to the base of the second transistor Q2 via the line 19. (Control terminal).

The transistor 17 controls the second transistor Q2 to be turned off in the case of an overcurrent, and is connected between the line 19 and the ground, that is, the other end of the power source 1 in FIG. The rectifying / smoothing circuit 14 is composed of a diode 14a and a capacitor 14b, and has an output line 8 of the current detector 5.
Is rectified and sent to one input terminal of the comparator 15.
The comparator 15 is a reference voltage source 1 connected to the other input terminal.
The reference voltage indicating the overcurrent of No. 6 and the output voltage of the rectifying / smoothing circuit 14 are compared, and the transistor 17 is turned on when the output voltage of the rectifying / smoothing circuit 14 becomes equal to or higher than the reference voltage. This turns off the second transistor Q2.

In the switching power supply device of FIG. 1, the first and second transistors Q1 and Q2 are shown in FIG.
It is turned on alternately as shown in FIG. Now, when the transistor Q1 is on, the power source 1 and the first transistor Q
A current flows through a circuit composed of 1 and a primary winding N1 having an inductance and a capacitor C1. This current is a current based on the series resonance of the primary winding N1 and the capacitor C1 and has a waveform similar to a sine wave, which enables zero current switching at turn-on and reduces switching loss. When the first transistor Q1 turns off,
Instead, the second transistor Q2 is turned on and the capacitor C1, the primary winding N1 and the second transistor Q2 are turned on.
Resonant current flows in the circuit consisting of. By repeating the above-mentioned operation, currents in the first and second directions alternately flow in the primary winding N1 of the output transformer T1, and corresponding output voltages are obtained in the secondary windings N2a and N2b. D3
, D4 and capacitor C4 are rectified and smoothed. FIG. 6 shows the first
And the collector-emitter voltages VCE1 and VCE2 of the second transistors Q1 and Q2, the collector currents Ic1 and Ic2, and the current In1 of the primary winding N1 of the output transformer T1. The current in the region E1 of the current In1 in FIG. 6 (E) is the parallel circuit composed of the DC power supply 1, the capacitor C2, the primary winding N1 and the resonant circuit composed of the capacitor C1, the capacitor C1, the capacitor C3 and the primary winding N1. It flows based on the resonant circuit. The current in the region E2 of the current In1 is the capacitor C of the above resonance circuit.
Instead of 3, it flows through diode D2. The current in the regions E3, E4 in the negative half-wave flows through the capacitor C1, the primary winding N1 and the capacitors C2 and C3, and then through the diode D1 instead of the capacitor C2.

In the device of FIG. 1, when the voltage of the output terminal 6 becomes higher than a predetermined value, the output frequency f2 of the VCO 11 of FIG. 2 becomes high and the first and second transistor Q
The on / off repetition frequency of 1 and Q2 becomes high. On the contrary, when the voltage of the output terminal 6 is lower than the predetermined value, the operation opposite to the above is performed.

The voltage V of the primary winding N1 of the output transformer T1
The amplitude of n1 changes depending on the on / off frequency f2 of the first and second transistors Q1 and Q2. FIG. 3 shows the response of the resonance circuit of the inductance Ln1 of the primary winding N1 and the capacitor C1. The transistor Q has a frequency higher than the natural resonance frequency f1 determined by Ln1 and C1.
When Q1 and Q2 are turned on and off, the response decreases.
FIG. 4 is for explaining this. When f2 shown in the first half of FIG. 4 is low, the amplitude of the voltage Vn1 of the primary winding N1 is large, but when f2 shown in the second half is high. Voltage V
The amplitude of n1 decreases. As a result, the frequency f of the VCO 11
Voltage control is achieved by controlling in the range of 2 to f2 '.

[0010]

By the way, in the device of FIG. 1, in order to perform overcurrent protection or current control, the primary winding N
The current detector is connected in series with 1. The current detector is not only costly, but also occupies a large area. Although a current detection resistor may be connected in series to the primary winding N1 instead of the current detector 5, it has the same drawbacks as the current detector 5, and also has the drawback that power loss occurs.

Therefore, an object of the present invention is to provide a resonance type switching power supply device which can reduce the cost and size of the current detecting means.

[0012]

SUMMARY OF THE INVENTION To achieve the above object, the present invention provides a resonance circuit connected to a DC power supply via a switching element, and an output for obtaining an output corresponding to the resonance current of the resonance circuit. In a resonance type switching power supply device having a circuit, a resonance voltage detection circuit that detects a resonance voltage of the resonance circuit, and an output current in the output circuit is controlled (for example, reduced) based on the voltage detected by the resonance voltage detection circuit. Or a circuit for controlling the switching element so as to perform the cutoff control). It is possible to detect the current of the resonance type switching power supply device of the modified half bridge type as described in claim 2. Further, as described in claim 3, a tertiary winding may be provided for current detection. Further, as described in claim 4, it is possible to detect the current of the half bridge type resonance type switching power supply device.

[0013]

The function and effect of the present invention are realized by paying attention to the fact that the voltage of the resonance circuit is proportional to the output power.
The voltage detection circuit of each claim obtains a detection voltage corresponding to the output power. This detected voltage corresponds to the output current when the output voltage is constant. Therefore, the output current can be known from the detected voltage, and the voltage detection circuit functions as a current detection means. According to the first, second, and fourth aspects, the special current detector is not required, and the cost and the size of the current detecting means can be reduced. In the third aspect, the tertiary winding is provided, but the cost is reduced and the miniaturization is achieved as compared with the case where the current detector is provided independently.

[0014]

[First Embodiment] Next, a resonance type switching power supply device according to a first embodiment of the present invention will be described with reference to FIG. However,
6, the same parts as those in FIG. 1 are designated by the same reference numerals and the description thereof will be omitted. In FIG. 6, the current detector 5 provided in FIG. 1 is omitted, and instead, the voltage of the resonance capacitor C1 is detected by the line 8 as a voltage detection circuit, and this detection voltage is sent to the control circuit 2. The other configuration of FIG. 6 is the same as that of FIG.
Is the same as In the resonance type switching power supply device having the configuration of FIG. 6, when the power of the load connected to the output circuit of the output stage of the secondary windings N2a and N2b, that is, the output terminal 6, increases,
In proportion to this, the voltage of the primary winding N1 and the capacitor C1
The rectified smoothing value or the peak-hold value of the voltage of the voltage increases.
If the voltage at the output terminal 6 is controlled to a constant value, the rectified output voltage of the capacitor C1 and the primary winding increases in proportion to the load current. That is, the peak value of the resonance current flowing in a sinusoidal manner in the series resonance circuit of the capacitor C1 and the primary winding N1 having the inductance L changes depending on the size of the load connected to the output terminal 6, and the output current changes. When it gets bigger,
The peak value of the resonance current increases, and the peak value of the voltage of the capacitor C1 or the primary winding N1 having an inductance also increases. Therefore, the voltage of the capacitor C1 is changed to the line 8
Current detection can be achieved with a simple configuration in which detection is performed by, and cost reduction and miniaturization are achieved. The voltage of the capacitor C1 detected on the line 8 is the rectifying / smoothing circuit 1 of FIG.
4 and the comparator 15 and the transistor 17 into the OFF control circuit to input the second transistor Q at the time of overcurrent.
Used for off control of 2.

[0015]

[Second Embodiment] Next, a resonance type switching power supply device of a second embodiment will be described with reference to FIG. However, in FIG. 7, the same parts as those in FIG. 1 are designated by the same reference numerals and the description thereof will be omitted. In this embodiment, the primary winding N1 is moved to the ground side, and the voltage of the primary winding N1 is detected by the line 8 and sent to the control circuit 2. Other than this in FIG. 7, FIG.
Is configured the same as. Since the rectified and smoothed voltage of the voltage of the primary winding N1 is proportional to the load current, it is possible to obtain the same effect as that of the second embodiment.

[0016]

[Third Embodiment] Next, a resonance type switching power supply device according to a third embodiment of the present invention will be described with reference to FIG.
However, in FIG. 8, the same parts as those in FIG. 1 are designated by the same reference numerals and the description thereof will be omitted. In this embodiment, the transformer T1 is provided with a tertiary winding N3 for current detection. This tertiary winding N3 is closely electromagnetically coupled to the primary winding N1. Therefore, a voltage proportional to the primary winding N1 is obtained at the tertiary winding N3. Therefore, the voltage of the tertiary winding N3 can be used in the same manner as the current detection by the primary winding N1 of the second embodiment.

In FIG. 8, the first and second transistors Q1
, Q2 of the on / off control circuit 2a and the second transistor Q2 of the off control circuit 2b are shown separately.
The on / off control circuit 2a in FIG. 8 shows a portion including the VCO 11, the waveform shaping circuit 12, and the NOT circuit 13 in FIG. The off control circuit 2b is provided in place of the portion including the rectifying / smoothing circuit 14, the comparator 15 and the transistor 17 in FIG.

The OFF control circuit 2b includes a rectifying / smoothing circuit 14 connected to the tertiary winding N3. The output terminal of the rectifying / smoothing circuit 14 is connected to the base of the transistor 17 via a Zener diode 16a functioning as a reference voltage source and a comparator. The transistor 17 is connected via a diode 31 between the base and the emitter of the second transistor Q2. In order to maintain the ON state of the transistor 17 at the time of overcurrent, the Zener diode 32 is connected in parallel to the power supply 1 through the resistor 33, the cathode of the Zener diode 32 is connected to the emitter of the latch transistor 34, and the latch transistor The collector of 34 is connected to the base of the transistor 17, and the base of the latching transistor 34 is connected to the collector of the transistor 17. A resistor 35 is connected between the output lines of the rectifying / smoothing circuit 14.

When the voltage of the tertiary winding N3 rises as the load current increases, the output voltage of the rectifying and smoothing circuit 14 also rises. When this exceeds the Zener voltage of the Zener diode 16a, the Zener diode 16a turns on. , The base current of the transistor 17 is supplied, which also turns on. As a result, the second transistor Q1 is turned off. When the transistor 17 is turned on, the latching transistor 34 is also turned on, the base current of the transistor 17 is supplied from the power source 1, and this on state is maintained.
The diode 31 blocks the base current of the second transistor Q2 from flowing through the emitter / base of the latching transistor 34.

In the third embodiment, the tertiary winding N3 is provided, but since it is integrated with the transformer T1, the cost and size can be reduced as compared with the case where the current detector 5 is provided alone as shown in FIG. It

[0021]

[Fourth Embodiment] Next, a resonance type switching power supply device of a fourth embodiment will be described with reference to FIG. However, in FIG. 9, the same parts as those in FIGS. 1 and 6 are designated by the same reference numerals, and the description thereof will be omitted. In the embodiment of FIG. 9, the first and second switching power supply circuits 4 are connected to one load 43.
1, 42 are connected in parallel. The first and second switching power supply circuits 41 and 42 have the same circuit configuration, and the first and second switching power supply circuits 41 and 42 are replaced by the first and second resonance capacitors C1 in FIG.
The resonance capacitors C1a and C1b are included. First and second
The series circuit of the resonance capacitors C1a and C1b is connected between one end and the other end of the power source 1, and the primary winding N1 having the inductance of the transformer T1 is connected between the first and second switching elements Q1 and Q2. It is connected between the connection midpoint and the interconnection midpoint of the first and second resonance capacitors C1a and C1b. Therefore, the circuit of FIG. 9 is formed in a half bridge type.

Instead of the transistors Q1 and Q2 of FIG. 6, the first and second switching elements Q1 and Q2 of FIG.
Insulation gate type (M
(OS type) field effect transistor, which is equivalent to the first and second control switches S1 and S between the drain and the source.
2 and a first and a second diode connected in anti-parallel thereto
Do Da and Db. The first and second switching elements Q1 and Q2 may be composed of a bipolar transistor and a diode connected in antiparallel to the bipolar transistor as shown in FIG. Further, capacitors C2 and C2 are arranged in parallel with the first and second switching elements Q1 and Q2 as in FIG.
3 can be connected.

First and second switching power supply circuits 4
Capacitors 46 and 47 are connected in parallel to the first resonance capacitor C1b via diodes 44 and 45 in order to detect the current supplied to the load 43 from the motors 1 and 42. In addition, a resistor 48 in parallel with the capacitors 46 and 47,
A series circuit of 49 and a series circuit of resistors 50 and 51 are connected. The current balance detection resistor 52 is connected between the voltage dividing points of the resistors 48 and 49 and the voltage dividing points of the resistors 50 and 51 which are set to have the same voltage dividing ratio. This current detection resistor 5
Both ends of 2 are connected to a current balance detecting differential amplifier 53, and its output terminal is connected to the control circuits 6a and 6b. The control circuits 6a and 6b are responsive to the output of an error amplifier (not shown) provided in the same manner as the error amplifier 3 of FIG. 1 for controlling the voltage of the load 43 to be constant. Controls the ON time width of Q1 and Q2. Further, the control circuits 6a and 6b are responsive to the output of the differential amplifier 53 so that the output currents of the first and second switching power supply circuits 41 and 42 are balanced so that the first and second switching elements Q1 and Q2 are balanced. Controls the on-time width. The output of the differential amplifier 53 changes depending on the current flowing through the resistor 52. When the output currents of the first and second switching power supply circuits 41 and 42 are the same, the voltages of the capacitors 46 and 47 are also the same, and the divided output of the resistors 48 and 49 and the divided voltage of the resistors 50 and 51 are the same. The outputs are also the same, and no current flows through the resistor 52. However, when the output current becomes unbalanced, the current flows through the resistor 52.

In the first and second switching power supply circuits 41 and 42 of FIG. 9, the series resonance is caused by the capacitance of the parallel circuit of the first and second resonance capacitors C1a and C1b and the inductance of the primary winding N1. Occurs.

Also in the circuit of FIG. 9, it is not necessary to connect a current detector to the main circuit through which the resonance current flows, as in the case of FIG. 6, and the same effect as that of the circuit of FIG. 6 can be obtained. Also,
The output current adjustment of the first and second switching power supply circuits 41 and 42 can be easily achieved.

[0026]

MODIFICATION The present invention is not limited to the above-mentioned embodiments, and the following modifications are possible. (1) Two different outputs can be obtained by changing the number of turns of the secondary windings N2a and N2b. Also, the output transformer T1
It is possible to omit one of the secondary windings N2a and N2b. (2) Transistors Q1 and Q2 of FIGS. 6, 7 and 8
Can be replaced with another switching element such as a field effect transistor. (3) Transistor Q2 in the circuits of FIGS.
The off control circuit of can be changed to the off control circuit 2b of FIG. On the contrary, the off control circuit 2b of FIG. 8 can be changed to the off control circuit of FIG. (4) The present invention can be applied to a case where the currents of the first and second transistors Q1 and Q2 are fed back using a mag-amplifier to control the first and second transistors Q1 and Q2 by self-excitation. it can. (5) The switching power supply circuits of FIGS. 6, 7, and 8 can be connected in parallel as shown in FIG. 9 to provide a current balance detection circuit similar to that of FIG. (6) In the circuits of FIGS. 6, 7, 8 and 9, 1
A resonance inductance can be connected in series with the secondary winding N1. Then, the output current can be known by detecting the voltage of the resonance inductance. Further, the inductance for resonance and the inductance of the primary winding may be summed to obtain a series resonance inductance. (7) In the circuits of FIGS. 6, 7, 8 and 9, 1
In parallel with the secondary winding N1, it is possible to connect an inductance of the primary winding N1 or an inductance larger than the inductance of the primary winding N1. (8) In FIG. 9, the capacitance of the capacitors C1a and C1b can be increased, and a resonance capacitor having a smaller capacitance than this can be connected in series to the primary winding N1. (9) In FIGS. 6, 7 and 8, the second transistor Q2 is controlled to be off by the voltage detection by the line 8 or the tertiary winding N3 to cut off the output current. It can be turned off, or the first and second transistors Q1, Q2 can be turned off. Further, by detecting the current by the line 8 or the tertiary winding N3, the ON time width of the first and second transistors Q1 and Q2 can be narrowed to reduce the output current.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a conventional switching power supply device.

FIG. 2 is a diagram showing a control circuit of FIG.

FIG. 3 is a diagram for explaining the relationship between the on / off frequencies of Q1 and Q2 and the response of the resonant circuit of N1 and C1 in FIGS. 1 and 6, 7 and 8.

[Fig. 4] ON / OFF frequency of Q1 and Q2 and primary winding N1
It is a figure which shows the relationship with the voltage of.

5 is a waveform diagram showing a state of each part of FIG.

FIG. 6 is a circuit diagram showing a switching power supply device according to a first embodiment.

FIG. 7 is a circuit diagram showing a switching power supply device according to a second embodiment.

FIG. 8 is a circuit diagram showing a switching power supply device according to a third embodiment.

FIG. 9 is a circuit diagram showing a switching power supply device of a fourth embodiment.

[Explanation of symbols]

 T1 output transformer N11a, N11b primary winding C1 resonance capacitor 2 control circuit

Claims (4)

[Claims] 1. A resonance type switching power supply device comprising: a resonance circuit connected to a DC power supply via a switching element; and an output circuit for obtaining an output corresponding to a resonance current of the resonance circuit. A resonance voltage detection circuit that detects a resonance voltage and a circuit that controls the switching element to control the output current in the output circuit based on the voltage detected by the resonance voltage detection circuit are provided. Resonant type switching power supply device characterized. 2. A DC power supply, first and second switching elements connected between one end and the other end of the DC power supply, and an output transformer including a primary winding and a secondary winding. , A series circuit of a resonance capacitor and an inductance and the primary winding, or a series circuit of a resonance capacitor and a primary winding having an inductance, which are connected in series to the first and second switching elements, respectively. And a control circuit for alternately turning on and off the first and second switching elements, wherein the resonance capacitor, the inductance, or the voltage of a primary winding having the inductance is detected. A voltage detecting circuit for controlling the current in the output stage of the secondary winding based on the voltage detected by the voltage detecting circuit. And a circuit for controlling the switching element of No. 2 are provided. 3. A DC power supply, first and second switching elements connected between one end and the other end of the DC power supply, and an output transformer including a primary winding and a secondary winding. A series circuit of a resonance capacitor and an inductance and the primary winding connected in series to the first and second switching elements, or a series circuit of a resonance capacitor and a primary winding having the inductance. A resonance type switching power supply device comprising a control circuit for alternately turning on and off the first and second switching elements, a tertiary winding tightly electromagnetically coupled to the primary winding, and a tertiary winding A voltage detection circuit for detecting the voltage of the line; and the first and / or second switching element for controlling the current in the output stage of the secondary winding based on the voltage detected by the voltage detection circuit. Times to control Resonant switching power supply apparatus characterized by bets is provided. 4. A series circuit of first and second switching elements connected between one end and the other end of a DC power supply, and a first and a second series connected between one end and the other end of the DC power supply. A series circuit of a second capacitor, an inductance connected between an interconnection midpoint of the first and second switching elements and an interconnection midpoint of the first and second capacitors, and a primary of a transformer A primary winding having a series circuit or an inductance with a winding, a secondary winding electromagnetically coupled to the primary winding, an output circuit connected to the secondary winding, the first and the first A resonance type switching power supply device comprising a control circuit for alternately turning on and off two switching elements, a voltage for detecting a voltage of the first or second capacitor, the inductance, or a primary winding having the inductance. A detection circuit; and a circuit for controlling the first and / or second switching element so as to control the current of the output circuit based on the voltage detected by the voltage detection circuit. Resonant type switching power supply device.