JPH118970A - Chopper circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make turn off loss of a switching element reliable by utilizing an auxiliary capacitor to be connected in parallel with a diode, and a required auxiliary winding to be connected in series with the switching element. SOLUTION: When a switching element 30 is tuned on, a current flows through a closed circuit of 10-20-25-30-20 to induce voltages having a positive pole shown at a black point in the inductor 20 and the auxiliary winding 25. The voltage of an auxiliary capacitor 45 is equal to the voltage of a smoothing capacitor 50 less the voltage of the auxiliary winding 25. When the switching element 30 is tuned off, current paths of 20-25 is switched to 20-45 and a current flows through a closed circuit of 10-20-45-50-10. Consequently, the voltage across the smoothing capacitor 50 and the auxiliary capacitor 45 is kept at a substantially invariant level during the turn off interval. Since the switching element 30 is held at a substantially invariant voltage level, even if it is turned off, and held at a substantially zero voltage level during a turn on interval, so that the turn off loss is minimized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a chopper circuit used as an active filter or the like.

[0002]

2. Description of the Related Art A rectifying power supply for rectifying an AC power supply voltage, a chopper inductor, a switching element for intermittently applying the rectified power supply voltage to the chopper inductor are provided, and the switching element is stored in the chopper inductor. 2. Description of the Related Art A chopper circuit including a diode that emits electromagnetic energy through the rectified power supply and a smoothing capacitor that is charged by receiving an output of the diode is known.

[0003]

The operation at the time of turning off the switching element will be considered. The diode is turned on in accordance with the turning off of the switching element. The switching element current during turn-off decreases,
The reduced amount passes through the diode which is being turned on.
The voltage of the smoothing capacitor is applied to the switching element that is being turned off via a diode. For this reason, the turn-off environment of the switching element is severe, and a large turn-off loss occurs. An object of the present invention is to reduce the turn-off loss of a switching element.

[0004]

The circuit of the present invention includes a rectified power supply for rectifying an AC power supply voltage. A chopper inductor is provided. A switching element for intermittently applying the rectified power supply voltage to the chopper inductor; A diode that emits electromagnetic energy stored in the chopper inductor via the rectified power supply. A smoothing capacitor that is charged by receiving the output of the diode. The present invention is based on the above chopper circuit. According to the present invention, there is provided an auxiliary capacitor connected in parallel with the diode. The auxiliary capacitor is connected directly or in parallel with the diode via the smoothing capacitor. An auxiliary winding connected in series with the switching element is provided. The auxiliary winding is magnetically coupled to a main winding of the chopper inductor. The connection polarity between the main winding and the auxiliary winding is defined as additive polarity. The same effect can be obtained by changing the auxiliary winding connected in series with the switching element and connecting the auxiliary winding in series with the auxiliary capacitor. However, in that case, the connection mode of the additional polarity is changed to a reduced polarity. The auxiliary capacitor acts to reduce the turn-off loss of the switching element. The auxiliary winding acts to reduce the turn-on loss of the switching element due to the use of the auxiliary capacitor.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIG. The illustrated circuit includes a rectified power supply 10 for rectifying an AC power supply 11 voltage. A chopper inductor 20 is provided. Rectifier power supply 10 voltage to chopper inductor 20
And a switching element 30 for intermittently applying a voltage to the switching element. A diode 40 is provided that emits electromagnetic energy stored in the chopper inductor 20 via the rectified power supply 10.
The smoothing capacitor 50 is charged by receiving the output of the diode 40. The present invention is based on the above chopper circuit. In the present invention, an auxiliary capacitor 45 connected in parallel with the diode 40 is provided. An auxiliary winding is connected in series with the switching element. The auxiliary winding 25 is magnetically coupled to the main winding of the chopper inductor 20. The connection polarity between the main winding (20) and the auxiliary winding 25 is defined as additive polarity. Supplement the structure description. 12-1
Reference numeral 5 denotes a rectifier diode belonging to the rectifier power supply 10 and constitutes a full-wave rectifier circuit. The switching element 30 is a transistor. Although the illustration of the control circuit of the switching element 30 is omitted, it turns on and off the switching element 30 appropriately so that the voltage of the smoothing capacitor 50 becomes substantially constant. Both ends of the smoothing capacitor 50 are DC output terminals to which a DC load (not shown) is connected. An example is an inverter for lighting a discharge lamp. The chopper inductor 20 has a transformer type structure in which the auxiliary winding 25 is attached. The connection polarity between the main winding and the auxiliary winding 25 of the chopper inductor 20 is an additive polarity, which is the polarity of the dot (black dot) shown in the figure. The auxiliary capacitor 45 acts to reduce the turn-off loss of the switching element 30. The auxiliary winding 25 acts to reduce the turn-on loss of the switching element 30 due to the use of the auxiliary capacitor 45. Hereinafter, these points will be described. During the period when the switching element 30 is turned on, 10-20-
A current flows through the closed circuit of 25-30-20. A voltage having a black dot as a positive electrode is induced in the chopper inductor 20 and the auxiliary winding 25 during the ON period. The voltage of the auxiliary capacitor 45 is a value obtained by subtracting the voltage of the auxiliary winding 25 from the voltage of the smoothing capacitor 50. When the switching element 30 is turned off, the current path of 20-25 is switched to 20-45,
A current flows through the closed circuit of 10-20-45-50-10. Not only the voltage of the smoothing capacitor 50 but also the voltage of the auxiliary capacitor 45 cannot be changed non-linearly and change continuously. For this reason, the voltage across the smoothing capacitor 50 and the auxiliary capacitor 45 is maintained almost constant during the turn-off short period. The same effect is obtained even when the auxiliary capacitor 45 is located at a position straddling the smoothing capacitor 50 and the diode 40. For this reason, the voltage across the rectified power supply 10 and the chopper inductor 20 is also maintained substantially constant. Of course, the voltage of the rectified power supply 10 is almost constant and unchanged. Therefore, the voltage of the chopper inductor 20 is also substantially constant. The voltage of the auxiliary winding 25 magnetically coupled to the chopper inductor 20 is also substantially constant. Therefore, the voltage of the switching element 30 is also substantially constant. That is, the switching element 30 is maintained at a substantially constant voltage level even when turned off, and maintains a substantially zero voltage level when turned on. Switching element 3
The turn-off loss of 0 becomes the current-voltage product during the turn-off, but the latter voltage is maintained at almost zero level. Therefore, the turn-off loss becomes very small. With the turning off of the switching element 30, 10-20-
Current flows through the closed circuit of 45-50-10. Accordingly, the electric charge of the auxiliary capacitor 45 is discharged. After the discharge is completed, a current flows through a closed circuit of 10-20-40-50-10. In the process, the polarities of the voltages of the chopper inductor 20 and the auxiliary winding 25 are inverted, and the voltage is changed to a voltage that makes the dot negative. Eventually, when the electromagnetic energy of the chopper inductor 20 becomes empty, the current becomes zero, and thereafter, the stationary state is maintained. The quiescent state continues until the switching element 30 is turned on. When the switching element 30 is turned on, current starts to flow in the closed circuit of 50-45-25-30-50. No current flows yet in the closed circuit of 10-20-25-30-10. Such operation is based on the fact that the voltage of the auxiliary capacitor 45 at the initial stage of turn-on is almost zero, and the voltage of the smoothing capacitor 50 is higher than the voltage of the rectified power supply 10 (characteristics of the step-up chopper circuit).
When the closed circuit of 50-45-25-30-50 is energized,
The auxiliary capacitor 45 charges and the voltage of the auxiliary winding 25 decreases. Eventually, the time is reached when the sum of the voltage of the auxiliary winding 25 and the voltage of the chopper inductor 20 is about to decrease below the rectified power supply 10 voltage. After that, 50-45-25-
The current in the closed circuit of 30-50 becomes zero, and
Current starts to flow through the closed circuit of -20-25-30-10. Thereafter, the operation described above is repeated. The role of the auxiliary capacitor 45 is to reduce the turn-off loss of the switching element 30. The role of the auxiliary winding 25 is to prevent a sharp charging current flowing through the auxiliary capacitor 45 from flowing when the switching element 30 is turned on. The auxiliary capacitor 45 contributes to the reduction of the turn-off loss, but tries to form a steep charging current by making it worse at the time of turn-on. The auxiliary winding 25 acts to alleviate the formation of such a steep charging current and suppress the turn-on loss. From the viewpoint of steep current blocking, the auxiliary winding 25 may be an independent inductor independent of the chopper inductor 20. However, if it is an independent inductor (25), the switching element 30 must accept and absorb the electromagnetic energy stored therein during the turn-on period at the next turn-off.
Then, since the turn-off loss cannot be reduced, it becomes impossible in the present invention. The room for deformation of the circuit in FIG. 1 will be described. The auxiliary capacitor 45 is connected in parallel with the diode 45 in FIG. However, it need not be straightforward. The auxiliary capacitor 45 may be connected in parallel with the diode 45 via the smoothing capacitor 50. In this case, the auxiliary capacitor 45 includes a diode 45 and a smoothing capacitor 5.
Straddles the whole of 0. Also in this case, the change in the voltage across the rectified power supply 10 and the inductor 20 for the chopper can be given continuity, which is the same effect. Although the auxiliary winding 25 is connected in series with the switching element 30 in FIG. 1, it may be connected in series with the auxiliary capacitor 45 instead.
When the role of the auxiliary winding 25 is turned on, the switching element 30 has a steep current (the charging current of the auxiliary capacitor 45 in the case of FIG. 1, and the auxiliary capacitor 45 is a smoothing capacitor 50).
(This is to prevent the flow of the discharge when it is located over the diode 40.) Under such circumstances, a voltage having the black dot as the positive electrode must be induced in the chopper inductor 20. For this reason, the connection polarity of the auxiliary winding 25 connected in series with the auxiliary capacitor 45 is reduced with respect to the chopper inductor 20.

[0006]

The present invention utilizes an auxiliary capacitor connected in parallel with a diode, for example, in series, and uses a required auxiliary winding connected in series with a switching element. According to this, the turn-off loss of the switching element can be reduced. In addition, an increase in turn-on loss can be suppressed, which generally contributes to reduction and mitigation of switching loss.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a chopper circuit according to the present invention.

[Explanation of symbols]

10: rectified power supply, 11: AC power supply, 20: chopper inductor, 25: auxiliary winding, 30: switching element,
40: diode, 45: auxiliary capacitor, 50: smoothing capacitor

Claims (2)

[Claims] A rectifying power supply for rectifying an AC power supply voltage;
A chopper inductor, a switching element for intermittently applying the rectified power supply voltage to the chopper inductor, and a diode for discharging electromagnetic energy accumulated in the chopper inductor via the rectified power supply. A chopper circuit including a smoothing capacitor charged by receiving an output of a diode, comprising: an auxiliary capacitor connected in parallel with the diode; an auxiliary winding connected in series with the switching element; Is magnetically coupled to a main winding of the chopper inductor, and a connection polarity between the main winding and the auxiliary winding is set to an additional polarity. 2. A rectifying power supply for rectifying an AC power supply voltage,
A chopper inductor, a switching element for intermittently applying the rectified power supply voltage to the chopper inductor, and a diode for discharging electromagnetic energy accumulated in the chopper inductor via the rectified power supply. A chopper circuit including a smoothing capacitor charged by receiving an output of a diode, comprising: an auxiliary capacitor connected in parallel with the diode; an auxiliary winding connected in series with the auxiliary capacitor; Is magnetically coupled to the main winding of the chopper inductor, and the connection polarity between the main winding and the auxiliary winding is reduced.