JP2021192565A - Power source device - Google Patents

Abstract

To provide a power source device enabling power conversion efficiency thereof to be improved.SOLUTION: A power source device 1 of the present embodiment includes: a transformer which includes a primary coil winding with one end thereof connected to a positive electrode of a DC power source, a secondary coil winding connected to a load; a first switching element connected between the other end of the primary coil winding and a negative electrode of the DC power source; a control circuit controlling the switching operation of the primary switching element; a first snubber circuit connected to the primary coil winding in parallel; a second snubber circuit connected to the one end of the primary coil winding; and a second switching element connected between the second snubber circuit and the other end of the primary coil winding. The control circuit switches on and off of the second switching element, according to the state of the load.SELECTED DRAWING: Figure 1

Description

Embodiments of the present invention relate to a power supply device.

A flyback type power supply device is known as a power supply device that supplies electric power to a load. The flyback type power supply unit is equipped with a snubber circuit as a protection circuit. The snubber circuit has a function of suppressing a surge voltage generated on the primary winding side of the transformer.

In a system with a power supply and a load connected to this power supply, the load state may switch. Such a system includes, for example, a steady load mode in which the power consumption of the load is relatively large, and a light load mode in which the power consumption of the load is relatively small. The power supply unit generally operates in a constant snubber circuit regardless of the load condition.

Since the circuit constant of the snubber circuit is a fixed value, when the steady load mode is switched to the light load mode, the clamping capacity of the snubber circuit becomes unoptimal and power is lost more than necessary. This reduces the efficiency of the power supply in the light load mode.

Japanese Patent No. 361838 Japanese Patent No. 3747746

An object to be solved by the present invention is to provide a power supply device capable of improving the power conversion efficiency.

The power supply device according to the embodiment includes a primary winding and a secondary winding, one end of the primary winding is connected to a positive electrode of a DC power supply, and the secondary winding is connected to a load. The transformer, the first switching element connected between the other end of the primary winding and the negative electrode of the DC power supply, the control circuit for controlling the switching operation of the first switching element, and the primary. A first snubber circuit connected in parallel to the winding, a second snubber circuit connected to one end of the primary winding, and a connection between the second snubber circuit and the other end of the primary winding. The second switching element is provided. The control circuit switches on and off of the second switching element according to the state of the load.

FIG. 1 is a circuit diagram of a power supply device according to an embodiment. FIG. 2 is a circuit diagram showing an example of the configuration of a snubber circuit. FIG. 3 is a flowchart illustrating an operation mode switching operation.

Hereinafter, embodiments will be described with reference to the drawings. Some embodiments shown below exemplify devices and methods for embodying the technical idea of the present invention, and the technical idea of the present invention is specified by the shape, structure, arrangement, etc. of the components. It is not something that will be done. In the following description, elements having the same function and configuration are designated by the same reference numerals, and duplicate description will be omitted.

[1] Configuration of Power Supply Device 10 The power supply device 10 according to the embodiment is a flyback type power supply device.

FIG. 1 is a circuit diagram of a power supply device 10 according to an embodiment. The system 1 provided with the power supply device 10 includes a DC power supply 2, a load 3, a switching element 4, and a load 5. The power supply device 10 includes terminals T1 and T2 on the input side, terminals T3 and T4 on the output side, a transformer 11, a switching element 12, a control circuit 13, two snubber circuits 14-1, 14-1, a switching element 15, and a diode. It includes 16, a capacitor 17, a current detection circuit 18, a feedback circuit 19, a voltage detection circuit 20, and a feedback circuit 21.

A DC power supply 2 is connected to the terminals T1 and T2 on the input side. That is, the terminal T1 is connected to the positive electrode of the DC power supply 2. The terminal T2 is connected to the negative electrode of the DC power supply 2. The DC power supply 2 generates a DC voltage.

The transformer 11 is an isolation transformer including a primary winding W1 and a secondary winding W2. The winding direction of the secondary winding W2 is opposite to the winding direction of the primary winding W1. One end of the primary winding W1 is connected to the terminal T1, and the other end of the primary winding W1 is connected to the switching element 12 via the connection node N1. The transformer 11 converts the primary voltage (voltage of the primary winding W1) into a secondary voltage (voltage of the secondary winding W2) proportional to the turns ratio of the primary winding W1 and the secondary winding W2. do.

The switching element 12 is composed of, for example, a MOSFET (Metal Oxide Semiconductor Field Effect Transistor) and is also composed of an N-channel MOSFET. One end (drain) of the current path of the switching element 12 is connected to the primary winding W1 of the transformer 11 via the connection node N1. The other end (source) of the current path of the switching element 12 is connected to the negative electrode of the DC power supply 2 via the terminal T2. A control signal PWM is supplied from the control circuit 13 to the control terminal (gate) of the switching element 12. The switching element 12 performs a switching operation based on the control of the control circuit 13 to switch the DC voltage supplied from the DC power supply 2. Then, the switching element 12 supplies a switching voltage to the primary winding W1 of the transformer 11.

The snubber circuit 14-1 is connected between the terminal T1 and the connection node N1. The snubber circuit 14-1 is a protection circuit for absorbing a transient high voltage (surge voltage) generated in the primary winding W1 when the switching element 12 is turned off.

FIG. 2 is a circuit diagram showing an example of the configuration of the snubber circuit 14-1. The snubber circuit 14-1 includes a resistor R, a capacitor C, and a diode D. That is, the snubber circuit 14-1 is composed of an RCD snubber circuit.

One end of the resistor R is connected to the terminal T1 and the other end of the resistor R is connected to the cathode of the diode D. One end of the capacitor C is connected to the terminal T1 and the other end of the capacitor C is connected to the cathode of the diode D. The anode of the diode D is connected to the connection node N1. The circuit constant of the snubber circuit is determined by the resistance value of the resistor and the capacitance value of the capacitor.

The snubber circuit 14-1 clamps the surge voltage by absorbing the surge voltage at the time of turn-off of the switching element 12 by the capacitor C and consuming it by the resistor R.

The snubber circuit 14-1 is not limited to the RCD snubber circuit, and an RC snubber circuit in which resistors and capacitors are connected in series, a ZD snubber circuit in which a Zener diode and a diode are connected in series, and the like may be used.

Returning to FIG. 1, one end of the snubber circuit 14-2 is connected to the terminal T1, and the other end of the snubber circuit 14-2 is connected to the connection node N1 via the switching element 15. The function and circuit configuration of the snubber circuit 14-2 are the same as those of the snubber circuit 14-1.

The switching element 15 is composed of, for example, an N-channel MOSFET. One end (drain) of the current path of the switching element 15 is connected to the snubber circuit 14-2, and the other end (source) of the current path of the switching element 15 is connected to the connection node N1. A switching signal SW is supplied from the control circuit 13 to the control terminal (gate) of the switching element 15. The switching element 15 is turned on / off based on the control of the control circuit 13. The switching element 15 can switch the connection (activation and deactivation) of the snubber circuit 14-2.

The anode of the diode 16 is connected to one end of the secondary winding W2 of the transformer 11. The diode 16 is a rectifying element and has a function of rectifying the secondary voltage generated in the secondary winding W2 of the transformer 11.

One end of the capacitor 17 is connected to the cathode of the diode 16, and the other end of the capacitor 17 is connected to the other end of the secondary winding W2 of the transformer 11. The capacitor 17 has a function of smoothing the voltage and current rectified by the diode 16.

One end of the current detection circuit 18 is connected to the cathode of the diode 16, and the other end of the current detection circuit 18 is connected to the terminal T3. The current detection circuit 18 detects the value of the current flowing through the load.

The feedback circuit 19 is connected to the current detection circuit 18. The feedback circuit 19 sends a feedback signal regarding the current value detected by the current detection circuit 18 to the control circuit 13. The feedback circuit 19 is composed of, for example, a photocoupler.

The load 3 is connected to the terminals T3 and T4. The load 5 is connected in parallel to the load 3. That is, in the present embodiment, two loads 3 and 5 are prepared, and it is possible to execute two types of operation modes according to the load state.

The switching element 4 is composed of, for example, an N-channel MOSFET. One end (drain) of the current path of the switching element 4 is connected to the terminal T3, and the other end (source) of the current path of the switching element 4 is connected to one end of the load 5. A load switching signal SW_load is supplied from the outside to the control terminal (gate) of the switching element 4. The switching element 4 can switch the connection (activation and deactivation) of the load 5 according to the load switching signal SW_load.

The voltage detection circuit 20 is connected to terminals T3 and T4. The voltage detection circuit 20 detects the voltage values applied to the load 3 and the load 5.

The feedback circuit 21 is connected to the voltage detection circuit 20. The feedback circuit 21 sends a feedback signal regarding the voltage value detected by the voltage detection circuit 20 to the control circuit 13. The feedback circuit 21 is composed of, for example, a photocoupler.

The control circuit 13 generates a control signal (pulse width modulation signal) PWM. The control signal PWM consists of continuous pulses. The control circuit 13 controls the switching operation of the switching element 12 by using the control signal PWM. Specifically, the control circuit 13 controls the duty ratio of the control signal PWM based on the voltage value detected by the voltage detection circuit 20. The duty ratio is the ratio of the pulse width to one cycle of continuous pulses. Then, the control circuit 13 controls the switching operation of the switching element 12 so that the voltage applied to the load 3 and the load 5 becomes the target voltage.

Further, the control circuit 13 generates a switching signal SW and controls the on / off of the switching element 15 by using the switching signal SW. Specifically, the control circuit 13 is a first mode (steady load mode) M1 in which the two loads 3 and the load 5 are activated based on the current value detected by the current detection circuit 18. It is determined whether only the load 3 is the activated second mode light load mode) M2. Then, the control circuit 13 controls on and off of the switching element 15, that is, activation and deactivation of the snubber circuit 14-2 according to the operation mode.

[2] Operation Next, the operation of the power supply device 10 configured as described above will be described.

The DC voltage output from the DC power supply 2 is input to the series connection circuit including the primary winding W1 of the transformer 11 and the switching element 12. In this state, the control circuit 13 supplies the control signal PWM to the gate of the switching element 12. As a result, the transformer 11 repeatedly stores and releases energy. That is, when the switching element 12 is turned on (conducting state), a DC voltage is applied to the primary winding W1 of the transformer 11. Then, while the switching element 12 continues to be in the ON state, the primary side current flowing through the primary winding W1 of the transformer 11 increases, and energy is stored in the transformer 11. At this time, a voltage in the direction opposite to that of the primary winding W1 is generated in the secondary winding W2. Since the diode 16 cuts off the voltage generated in the secondary winding W2, no induced current flows in the secondary winding W2.

Subsequently, when the switching element 12 is turned off (cut off state), an electromotive force is generated on the secondary winding W2 side of the transformer 11, and energy is supplied from the transformer 11 to the secondary circuit side. At this time, a current passing through the secondary winding W2 side and the diode 16 flows through the capacitor 17. Then, the switching element 12 repeatedly turns on and off, so that a DC voltage is supplied to the load 3 and the load 5.

The voltage detection circuit 20 detects the voltage values applied to the load 3 and the load 5. The control circuit 13 controls the duty ratio of the control signal PWM so that the voltage value detected by the voltage detection circuit 20 becomes the target voltage.

Next, the operation mode switching operation will be described. The power supply device 10 according to the present embodiment can execute the first mode (steady load mode) M1 and the second mode (light load mode) M2.

In the first mode M1, the load switching signal SW_load is activated, and the switching element 4 is turned on. That is, the load 3 and the load 5 are connected to the terminals T3 and T4. In the first mode M1, the power consumption of the load is relatively large.

In the second mode M2, the load switching signal SW_load is deactivated, and the switching element 4 is turned off. That is, only the load 3 is connected to the terminals T3 and T4. The load power consumption of the second mode M2 is relatively small, and the load power consumption is smaller than that of the first mode M1.

FIG. 3 is a flowchart illustrating an operation mode switching operation.

The current detection circuit 18 detects the current value flowing through the load 3 and the load 5 via the terminal T3. The current value detected by the current detection circuit 18 is supplied to the control circuit 13 via the feedback circuit 19.

The control circuit 13 monitors information on the current value supplied from the current detection circuit 18 and the feedback circuit 19 (step S100).

Subsequently, the control circuit 13 determines whether or not the current value detected by the current detection circuit 18 is equal to or greater than the threshold value (step S101). The threshold used in step S101 separates the first current that flows when the load 3 and the load 5 are connected to the terminals T3 and T4 from the second current that flows when only the load 3 is connected to the terminals T3 and T4. It is a possible current value and is set between the first current and the second current.

When the current value is equal to or greater than the threshold value (step S101 = Yes), the control circuit 13 executes the first mode M1 (step S102). That is, the control circuit 13 activates the switching signal SW and turns on the switching element 15. As a result, the snubber circuit 14-1 and the snubber circuit 14-2 are connected in parallel to the primary winding W1 of the transformer 11, respectively.

When the current value is less than the threshold value (step S101 = No), the control circuit 13 executes the second mode M2 (step S103). That is, the control circuit 13 deactivates the switching signal SW and turns off the switching element 15. As a result, only the snubber circuit 14-1 is connected in parallel to the primary winding W1 of the transformer 11.

The snubber circuits 14-1 and 14-2 convert the energy returned to the primary circuit of the transformer 11 into heat when the switching element 12 is turned off, respectively. As a result, the surge voltage generated in the primary circuit can be reduced.

Further, the circuit constant of the snubber circuit can be adjusted according to the load state. That is, in the case of the first mode M1 having a large load, the snubber circuit 14-1 and the snubber circuit 14-2 are respectively connected in parallel to the primary winding W1. On the other hand, in the case of the second mode M2 where the load is small, only the snubber circuit 14-1 is connected in parallel to the primary winding W1. The circuit constant including the snubber circuit 14-1 and the snubber circuit 14-2 is optimally set for the first mode M1 which is a steady load. The circuit constants of the snubber circuit 14-1 are optimally set for the second mode M2, which is a light load.

[3] Effect of Embodiment As described in detail above, according to the embodiment, only the first mode (steady load mode) M1 in which two loads 3 and 5 are activated and one load 3 are active. The circuit constant of the snubber circuit can be changed in the second mode (light load mode) M2. Specifically, the power supply device 10 includes two snubber circuits 14-1 and 14-2, activates the snubber circuits 14-1 and 14-2 in the first mode M1, and activates the snubber circuits 14-1 and 14-2 in the second mode M2. , Only the snubber circuit 14-1 is activated.

As a result, the circuit constant of the snubber circuit can be optimally set according to the operation mode. Further, since the loss of the snubber circuit can be adjusted according to the operation mode, the power conversion efficiency of the power supply device 10 can be improved.

Further, the power supply device 10 includes a current detection circuit 18 that detects a current flowing through the load. Then, the control circuit 13 uses the current value detected by the current detection circuit 18 to select the load state, that is, which of the two operation modes (first mode M1 and second mode M2) is selected. Can be determined.

Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other embodiments, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are also included in the scope of the invention described in the claims and the equivalent scope thereof.

1 ... system, 2 ... DC power supply, 3 ... load, 4 ... switching element, 5 ... load, 10 ... power supply device, 11 ... transformer, 12 ... switching element, 13 ... control circuit, 14-1 ... snubber circuit, 14- 2 ... Snubber circuit, 15 ... Switching element, 16 ... Diode, 17 ... Condenser, 18 ... Current detection circuit, 19 ... Feedback circuit, 20 ... Voltage detection circuit, 21 ... Feedback circuit.

Claims (8)

A transformer comprising a primary winding and a secondary winding, one end of the primary winding being connected to the positive electrode of a DC power source and the secondary winding being connected to a load.
A first switching element connected between the other end of the primary winding and the negative electrode of the DC power supply,
A control circuit that controls the switching operation of the first switching element,
A first snubber circuit connected in parallel to the primary winding,
A second snubber circuit connected to one end of the primary winding,
A second switching element connected between the second snubber circuit and the other end of the primary winding,
Equipped with
The control circuit is a power supply device that switches on and off of the second switching element according to the state of the load. A first detection circuit for detecting the current flowing from the secondary winding to the load is further provided.
The power supply device according to claim 1, wherein the control circuit controls the second switching element based on a current value detected by the first detection circuit. The control circuit turns on the second switching element when the current value detected by the first detection circuit is equal to or more than the threshold value, and when the current value is less than the threshold value, the second switching element is turned on. The power supply device according to claim 2. The power supply device according to claim 2 or 3, further comprising a feedback circuit that feeds back the current value detected by the first detection circuit to the control circuit. A second detection circuit for detecting the voltage applied to the load is further provided.
The power supply device according to any one of claims 1 to 4, wherein the control circuit controls a switching operation of the first switching element based on a voltage value detected by the second detection circuit. The power supply device according to any one of claims 1 to 5, further comprising a diode having an anode connected to one end of the secondary winding and a cathode connected to the load. The power supply device according to any one of claims 1 to 6, further comprising a capacitor connected in parallel to the secondary winding. The power supply device according to any one of claims 1 to 7, wherein each of the first and second snubber circuits includes a resistor and a capacitor.

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