JP3414129B2 - Power supply - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a switching power supply device, and more particularly to a power supply device in which a chopper circuit and an inverter circuit also serve as switching elements.

[0002]

2. Description of the Prior Art FIG.
4776) circuit diagram. In this circuit, the switching element Q2 is shared by the boost chopper circuit for improving the input power factor and the inverter circuit for limiting the load current. The circuit configuration will be described below. AC power supply P
Is connected to the AC input terminal of the full-wave rectifier DB via the filter circuit F. A series circuit of an inductor LI and a switching element Q2 is connected to the DC output terminal of the full wave rectifier DB. The series circuit of the switching elements Q1 and Q2 is connected in parallel with the series circuit of the smoothing capacitors C1 and C2, and between the connection point of the switching elements Q1 and Q2 and the connection point of the smoothing capacitors C1 and C2, A series circuit of the inductor LM and the load circuit Z is connected. The switching elements Q1 and Q2 have a power M, for example.
It is composed of an OSFET, and a parasitic reverse diode is connected in parallel between its drain and source. A high-frequency drive signal is supplied between the gate and the source from a control circuit (not shown), and the switching elements Q1 and Q2 are alternately turned on / off.

The operation of the conventional circuit shown in FIG. 8 will be described with reference to FIGS. 9 and 10. First, when the switching element Q1 is turned off and the switching element Q2 is turned on, the inductor LM
The regenerative current due to the stored energy of the inductor is the inductor LM, the load circuit Z, the smoothing capacitor C2, the switching element Q2.
A current flows in the path of (the reverse diode of), and then the smoothing capacitor C2, the load circuit Z, the inductor LM, and the switching element Q2. Also, AC power supply P, filter circuit F, full-wave rectifier DB, inductor L
A current flows through the path of I and the switching element Q2, and energy is stored in the inductor LI. The current path at this time is shown in FIG. Next, when the switching element Q2 is turned off and the switching element Q1 is turned on, the ac energy stored in the inductor LI causes the AC power supply P, the filter circuit F, the full-wave rectifier DB, the inductor LI, and the switching element Q1 (reverse direction diode). , Smoothing capacitor C
A current flows through the path of C1 and C2, and the smoothing capacitor C1
C2 is charged. In addition, the regenerative current due to the stored energy of the inductor LM is the inductor LM, the switching element Q1 (a diode in the reverse direction), the smoothing capacitor C1,
It flows through the path of the load circuit Z and then the smoothing capacitor C
The current flows through the path of 1, the switching element Q1, the inductor LM, and the load circuit Z. The current path at this time is shown in FIG.
Shown in.

[0004]

In the conventional example circuit of FIG. 8 described above, the switching element Q2 is composed of a step-up chopper circuit for improving the input power factor and an inverter circuit for driving the load circuit.
The number of switching elements can be reduced as compared with the case where each of them is provided as a separate circuit. However, since a current obtained by superposing the current of the boost chopper circuit and the current of the inverter circuit flows through the switching element Q2, the withstand capability of the switching element Q2 increases and the cost reduction effect due to the decrease in the number of elements diminishes. Further, since the control signals for the boost chopper circuit and the inverter circuit are the same, the independence of control of each circuit is lost. In particular, when the load circuit resistance is low and it is desired to increase the load circuit current, the input power becomes excessive with respect to the output power, and the power applied to the parts increases.

The present invention is intended to solve such a problem, and an object thereof is to use not only the switching elements of the step-up chopper circuit and the inverter circuit but also the inductor, thereby making it more effective. (EN) Provided is a power supply device which realizes further cost reduction, and when the load circuit resistance is low and the load circuit current is increased, the input power does not become excessive with respect to the output power and the safety is improved. Especially.

[0006]

According to the present invention, in order to solve the above-mentioned problems, as shown in FIG. 1, first and second switching elements Q1 having reverse conduction paths are provided.
A circuit formed by connecting Q2 in series so that the forward directions thereof coincide with each other and a series circuit of two smoothing capacitors C1 and C2 are connected in parallel, and the first and second switching elements Q1 and Q2 are connected.
Is connected to one end of the inductor LM, and a load circuit Z is connected between the connection point of the smoothing capacitors C1 and C2 and the other end of the inductor LM. Connect to one end of the DC output terminal of the full-wave rectifier DB, and connect the other end of the DC output terminal of the full-wave rectifier DB to 2
The smoothing capacitors C1 and C2 are connected to either end of the series circuit, and the AC input terminal of the full-wave rectifier DB is connected to the AC power supply P via the filter circuit F.
It has a control means for alternately turning on / off the first and second switching elements Q1, Q2 at a frequency higher than the power supply frequency.

[0007]

1 is a circuit diagram showing a preferred embodiment of the present invention. In this circuit, not only the switching element Q2 but also the inductor LM is shared by the chopper circuit and the inverter circuit. The circuit configuration will be described below. The series circuit of the switching elements Q1 and Q2 is connected in parallel with the series circuit of the smoothing capacitors C1 and C2, and between the connection point of the switching elements Q1 and Q2 and the connection point of the smoothing capacitors C1 and C2, A series circuit of the inductor LM and the load circuit Z is connected. One end of the inductor LM has switching elements Q1, Q
The other end of the connection point is connected to one end of the DC output terminal of the full-wave rectifier DB through the high speed diode D1. The other end of the DC output terminal of the full-wave rectifier DB is connected to one end (negative electrode in the figure) of the series circuit of the smoothing capacitors C1 and C2. The AC power supply P is connected to the AC input terminal of the full-wave rectifier DB via the filter circuit F. Each of the switching elements Q1 and Q2 is composed of a power MOSFET, and a parasitic reverse diode is connected in parallel between its drain and source. A high-frequency drive signal is supplied between the gate and the source from a control circuit (not shown), and the switching elements Q1 and Q2 are alternately turned on / off.

The operation of the circuit of FIG. 1 will be described below with reference to FIGS. In this circuit, the load voltage Vz changes, and Vz = Vc− | Vin | with respect to the charging voltage Vc of the smoothing capacitors C1 and C2 and the input voltage Vin from the AC power supply P.
The mode is switched depending on whether or not Vz <Vc− | Vin |. The basic operation is to use smoothing capacitors C1 and C2 as the power source and switching elements Q1 and Q2.
2. The half-bridge inverter circuit composed of the inductor LM and the commercial power supply P are used as power sources, and the inductor LM,
This is the operation of the boost chopper circuit composed of the switching element Q2 and the parasitic diode of the switching element Q1.

First, in mode 1, the switching element Q
1 is on, current flows through the path of the smoothing capacitor C1, the switching element Q1, the inductor LM, and the load circuit Z, and energy is supplied from the smoothing capacitor C1 to the load circuit Z (FIG. 2).

In mode 2, the switching element Q1 is turned off and the switching element Q2 is turned on. However, due to the energy stored in the inductor LM in mode 1, the inductor LM, the load circuit Z, the smoothing capacitor C2 and the switching element Q2 are reversed. Current flows in the path of the directional diode, and energy is released to the load circuit Z and the smoothing capacitor C2 (FIG. 3).

In mode 3, since the switching element Q2 is on and the energy of the inductor LM is lost, a current flows through the smoothing capacitor C2, the load circuit Z, the inductor LM, and the switching element Q2, and the smoothing capacitor C2 is discharged. Energy is supplied to the load circuit Z (FIG. 3). In the above three modes, the load voltage V
Since z is low and Vz <Vc− | Vin |, the voltage Vd of the diode D1 is Vd = Vc−Vz− | Vin.
A potential of | is generated and energy does not flow from the AC power supply P side.

In mode 4, the switching element Q2 is on, the load voltage Vz rises, and Vz = Vc- | Vi.
In the case of n |, the energy flows in from the AC power supply P side, and the AC power supply P, the filter circuit F, the full-wave rectifier DB,
Diode D1, inductor LM, switching element Q
The step-up chopper operation in which current flows through the path 2 and the half-bridge inverter operation in which current flows through the path of the smoothing capacitor C2, the load circuit Z, the inductor LM, and the switching element Q2 are combined (FIG. 4).

In mode 5, the switching element Q2 is turned off and the switching element Q1 is turned on, but Vz = Vc
Between-| Vin | Operation, inductor LM, switching element Q
The half bridge inverter operation in which current flows in the reverse diode 1, the smoothing capacitor C1, and the load circuit Z is also used (FIG. 5). The load voltage Vz decreases and Vz <
When it becomes Vc- | Vin |, the inflow of energy from the AC power supply P side is stopped.

In mode 6, the switching element Q1 is on, but due to the energy stored in the inductor LM, a half current flows through the inductor LM, the reverse diode of the switching element Q1, the smoothing capacitor C1, and the load circuit Z. It is only a bridge inverter operation (Fig. 2).

In the case where the load impedance is low and a large current must be output, which is a problem in the conventional example, in the circuit of FIG. 1, the load voltage | Vz | does not rise, so Vc- | Vin | is not reached or V
The period in which z = Vc− | Vin | is shortened. As a result, whether the AC power source P has a period for storing energy in the inductor LM and a period for charging the smoothing capacitors C1, C2 with the energy stored in the inductor LM,
Or the period becomes short. That means AC power supply P
Of energy is not charged in the smoothing capacitors C1 and C2, or the amount of charge is reduced, and it is possible to prevent the voltage Vc of the smoothing capacitors C1 and C2 from rising abnormally.

[0016]

EXAMPLE The example of FIG. 6 is an example in which the present invention is applied to a discharge lamp lighting device. The difference is that in the circuit of FIG.
The point is that the discharge lamp DL is used for the load circuit Z and the small capacity capacitor C3 is connected in parallel. An inductor may be connected in series to the discharge lamp DL. The operation of the circuit is similar to that of the circuit of FIG.

Further, the embodiment of FIG. 7 is an example in which the full-wave rectifier DB of the embodiment of FIG. 6 is composed of high speed diodes, and the high speed diode D1 in the embodiment of FIG. 6 can be omitted.

[0018]

According to the present invention, not only the switching elements of the boost chopper circuit and the inverter circuit but also the inductors are used together, so that the number of inductor elements can be increased without increasing the current of the switching elements as compared with the prior art. And the voltage applied to the components can be prevented from rising when the load circuit has a low impedance.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a basic circuit configuration of the present invention.

FIG. 2 is a circuit diagram for explaining a first current path of the circuit of FIG.

FIG. 3 is a circuit diagram for explaining a second current path of the circuit of FIG.

FIG. 4 is a circuit diagram for explaining a third current path of the circuit of FIG.

5 is a circuit diagram for explaining a fourth current path of the circuit of FIG.

FIG. 6 is a circuit diagram showing an embodiment of the present invention.

FIG. 7 is a circuit diagram showing another embodiment of the present invention.

FIG. 8 is a circuit diagram showing a circuit configuration of a conventional example.

9 is a circuit diagram for explaining a first current path of the circuit of FIG.

FIG. 10 is a circuit diagram for explaining a second current path of the circuit of FIG.

[Explanation of symbols]

P AC power supply DB full wave rectifier Q1 switching element Q2 switching element LM inductor C1 smoothing capacitor C2 smoothing capacitor Z load circuit F filter circuit

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) H02M 7/48 H02M 7/21 H02M 7/5387 H05B 41/24

Claims (4)

(57) [Claims] 1. A first and a second having reverse conduction paths.
Circuit in which two switching elements are connected in series so that their forward directions coincide with each other, and a series circuit of two smoothing capacitors are connected in parallel, and one end of an inductor is connected to a connection point of the first and second switching elements. Then, connect a load circuit between the connection point of the smoothing capacitor and the other end of the inductor, connect the connection point of the load circuit and the inductor to one end of the DC output terminal of the full-wave rectifier, and connect the DC of the full-wave rectifier. A power supply device characterized in that the other end of the output terminal is connected to one end of either of the series circuits of two smoothing capacitors, and the AC input terminal of the full-wave rectifier is connected to an AC power supply via a filter circuit. 2. The power supply device according to claim 1, wherein the load circuit is an inductive load. 3. The power supply device according to claim 2, wherein a small-capacity capacitor is connected in parallel with the inductive load. 4. A frequency higher than the power supply frequency of the AC power supply.
Alternately turns on the first and second switching elements at the wave number
A control means for turning off is provided.
4. The power supply device according to any one of 3 to 3 .