JPS585433Y2 - transistor converter - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a transistor converter, and particularly relates to a transistor converter with insulation between input and output.

FIG. 1 shows a conventional transistor converter, in which there is one main transistor.

The main DC power supply connects the commercial AC input to the diode bridge D1.
It is rectified by C1 and smoothed by capacitor C1 to obtain a DC output.

The main transistor Q1 is connected to the main transformer T1 from the main DC power supply.
The average power supplied to the switch is controlled by the switch operation.

Note that the capacitor C2 and the resistor R1 define the oscillating current of the main transformer T1, and the capacitor C3 and the resistor R2 are absorbers for preventing spike voltage.

The rectifying and smoothing circuit rectifies the output current of the main transformer T1 through the diode D2 while the main transistor Q1 is on, and transfers the energy stored in the choke coil L1 to the capacitor C4 through the diode D3 when the main transistor Q1 is off, thereby producing a DC output. obtain.

The control circuit CON uses the DC output of the rectifying and smoothing circuit as a sense input, and controls the on/off ratio of the main transistor Q1.

Here, in order to insulate between the AC input and the DC output, the control circuit CON is isolated from the AC input side.

That is, the power necessary for the control operation of the control circuit COH is obtained from AC input via the commercial frequency transformer T2, and the control output is provided to the base of the main transistor Q1 via the pulse transformer T3.

In this case, a large amount of control power is required to drive the main transistor Q1, and as a result, a commercial frequency transformer T2 with a large rated power and a DC power source for the control circuit are required, and the weight thereof is also increased.

As a countermeasure to this problem, there is a method of using a switching type DC power supply for the control circuit to reduce its size, but the power supply circuit becomes complicated.

Another method is to insulate the DC sense input to the control circuit CON with a photocoupler, and both transformers T2. Although there is a method in which T3 is omitted, the characteristics of the photocoupler change significantly over time, and the control characteristics of the DC output deteriorate.

The purpose of this invention is to provide a transistor converter that can reduce the size of a commercial frequency transformer for a control circuit and a DC power supply for a control circuit without complicating the configuration or reducing control performance.

FIG. 2 is a circuit diagram showing an embodiment of this invention, and parts that are the same as those in FIG. 1 or have the same functions are designated by the same reference numerals.

In FIG. 2, the control circuit CON has a control output that is a small current, small voltage signal, and accordingly, the commercial frequency transformer T2, the pulse transformer T3, the DC power supply for the control circuit, and the miniaturization and weight reduction of the control circuit. is being carried out.

Control power necessary for driving the main transistor Q1 is obtained from a drive circuit provided on the main DC power supply side.

That is, the drive circuit corresponding to the output section of the control circuit CON includes capacitors C5, C6, diodes D4 . D5, transistor Q2, Zener diode D6 and resistor R3°R
4, R5, etc., and drives the main transistor Q1 on and off in response to a control signal from the control circuit CON.

Here, the drive circuit obtains the power necessary for its operation directly from the main DC power supply at the beginning of converter operation (the first rise of the control signal), and thereafter from the feedback winding N3 provided in the main transformer T1. I have configured it so that I can get it.

This operation will be explained with reference to FIG. First, when an AC input is applied, the voltage of the main DC power supply (Fig. 3 A) begins to rise, and capacitor C6 is connected to the main DC power supply via capacitor C5 for fast rises, and for slow rises of the main DC power supply. Charged through high resistance R3 and diode D4 (Figure 3)
When the anode potential of the diode D4 reaches the Zener voltage of the Zener diode D6, charging is stopped.

In this state, when a control signal (Fig. 3 C) is applied from the control circuit CON via the pulse transformer T3, the transistor Q2 is turned on, and the charge stored in the capacitor C6 is transferred via the resistors R4, R5 and the transistor Q2. flows into the base of the main transistor Q1, and the main transistor Q1
turns on.

When the main transistor Q1 is turned on, each winding Nl, N2 . A voltage is generated in N3, a main DC current is obtained from the winding N2, and the voltage of the winding N3 (Fig. 3-2) drives the main transistor Q1 through positive feedback through the diode D5, resistor R5, and transistor Q2, and also drives the main transistor Q1 through the diode D5, resistor R5, and transistor Q2. D5 charges the capacitor C6 via the resistor R4.

When the control signal from the pulse transformer T3 is released, the transistor Q2 is turned off, and the main transistor Q1 is also turned off.However, since the capacitor C6 does not have a discharge circuit, it remains charged for a long period of time at a level of self-discharge. , is discharged at the initial stage when the control signal is applied again, and then charged by the output current of the feedback winding N3.

Therefore, the capacitor C6 only needs to be discharged for 1 to 2 .mu.s before charging starts by the feedback winding N3, and may have a small capacity, and its initial charging circuit (for example, a Zener diode) may also have a small capacity.

Further, since there are two paths for charging the capacitor C6 at the initial stage of converter operation: the path of the capacitor C5 and the path of the resistor R3 and the diode D4, stable startup can be performed at any rise of the AC input.

Note that in the above embodiment, one main transistor Q1
Although the case where the main transformer T1 is driven is shown in the above, it can also be applied to a bridge type converter having four main 1-transistors and a push-pull type converter having two main 1-transistors.

As explained above, the transistor converter of this invention reliably obtains enough power from the main DC power supply to turn on the main transistor Q1 when the first control signal is applied, and then the feedback winding of the main transformer. Since the control circuit CON is equipped with a drive circuit for driving the main transistor, which obtains the necessary power from the , can be made lightweight.

Further, since the power required for the drive circuit is obtained from the feedback winding of the main I-lance except during startup, the DC power supply for the drive circuit can also be made smaller and lighter.

[Brief explanation of the drawings] Figure 1 is a circuit diagram showing a conventional transistor converter.
FIG. 2 is a circuit diagram showing an embodiment of the transistor converter according to this invention, and FIG. 3 is a time chart for explaining the operation of FIG. 2. T1: Main transformer, T2: Commercial frequency transformer, T3: Hals transformer, Ql: Main transistor, CON: Control circuit, Q2: Auxiliary transistor, N3: Feedback winding, D6:
zener diode.

Claims (1)

[Scope of utility model registration request] A main DC power supply that obtains a DC output from an AC input, a main transistor that uses switch operation to control the average power supplied from the main DC power supply to the main transformer, a rectifier and smoothing circuit that obtains a DC output from the output current of the main transformer, and an AC A control circuit that obtains power from an input via an isolation transformer, uses the DC output of the rectifier and smoothing circuit as a sense input, and sends a control signal for the main transistor via the isolation transformer, and a control signal from this control circuit. an auxiliary transistor that drives the main transistor according to the auxiliary transistor, a capacitor (first capacitor) provided as a power supply source for driving the main transistor via the auxiliary transistor, and a charging circuit that charges the capacitor. The charging circuit includes a Zener diode connected to the main DC power supply via a resistor, and a first capacitor connected in parallel to the Zener diode.
a second capacitor that connects the first capacitor in parallel to the main DC power supply, and a second diode that connects the first capacitor in parallel to a feedback winding provided in the main transformer. A transistor converter characterized by: