JPS6331472A - High-frequency high-voltage dc power source - Google Patents

Abstract

PURPOSE:To perform a reduction in size and a high frequency switching of a high-frequency high-voltage DC power source by turning on and off a switching element of an inverter by a zero-cross signal. CONSTITUTION:A controller CONT of an inverter 2 has an inverter-current detecting current-transformer CT1, a bridge rectifier DB1, connected to CT1, a comparator IC1, a differentiator CD.Rd, a J-K flip-flop IC5, a gate driving IC, a voltage to frequency converter V/F etc. Transistors Q1-Q4 of a circuit 2 are turned on and off synchronously with the fundamental frequency of switching obtained by converting a detected DC output signal by the converter V/F. The detected signal from the transformer CT1 is compared with a reference voltage Er by the comparator IC1, and a trigger signal is generated upon zero- crossing of the inverter current. This is repeated at every half period to perform a high-speed switching.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a high frequency DC high voltage power supply circuit. An example of the circuit configuration of a conventional high frequency DC high voltage power supply circuit is shown in FIG. Figure 1 shows a rectifier circuit 1 that rectifies AC input, an inverter circuit section 2 that converts DC into high-frequency AC, a step-up transformer 3, a high voltage rectifier circuit section 4, a DC filter circuit 5, a control circuit section 6, and a load 7. The inverter circuit section 2 is a high frequency DC high voltage power supply circuit.
Possible configurations include (1) full bridge configuration, (2) half bridge configuration, and (3) push-pull configuration shown in the figure. or,
The inverter circuit section 2 may also have a configuration including a pre-leg, rake section 8 and an inverter switch section 9 as shown in FIG.

As an example of the radar section 8, the step-down converter shown in FIG.
) to (3). SW,,S～V,～S
W is a semiconductor switch such as a transistor, thyristor, or MO8FgT, C11, C12, CI, and C2 are capacitors, and D is a diode. A desired output was obtained by detecting the voltage or current of the load and sending a PWM control signal from the control circuit section 6 to the inverter circuit section 2. In the conventional circuit, the step-up transformer 3 shown in FIG. 1 is replaced by the step-up transformer 3 shown in FIG.
), and as the step-up ratio n increases, the equivalent circuit of the step-up transformer is shown in Figure 5 (b), and its voltage step response is as shown in Figure 6, when the load is light. It becomes vibratory. Therefore, if the current waveform also oscillates and the natural frequency is close to or lower than the switching frequency of the inverter circuit, it is difficult to perform normal PWM control of the inverter circuit. Moreover, it was also an obstacle to miniaturization of DC power supplies.

It is an object of the present invention to solve this problem and enable high frequency switching. FIGS. 7 and 8 are circuit diagrams of one embodiment of the present invention and three diagrams showing the operation of each part thereof, and the same reference numerals as in the conventional example indicate equivalent parts. C0NT in the figure
1 is a current transformer CT that detects an inverter circuit current in a control circuit section that constitutes a main part of the present invention.

Bridge rectifier circuit DBI, comparator Ice, capacitor CD and resistor FLD forming a differentiation circuit, inverter IC
,, J-, flip-flop IC, gate drive (IC) IC, IC4 and voltage frequency conversion circuit V/F
It is formed by etc. Note that, considering a constant current mmi in which the output current is constant, when the inverter circuit unit 2 is configured as shown in (1) to (3) in FIG. 4, the output current is controlled by a frequency adjustment method. Further, in the case of the pre-regulator system (FIG. 2), if a step-down converter (FIG. 3) is employed as the pre-regulator, the output voltage is controlled to obtain the desired constant current output. This circuit operation changes the frequency of the inverter circuit section 2 (full bridge configuration) to a constant current output when the DC output current (
Figure 8 (a)) is detected by the shunt resistor RH and frequency converted by the voltage/frequency conversion circuit V/F to obtain a switching reference oscillation waveform proportional to the output ti as shown in Figure 8 (bl). (b ) The transistors Ql and Q2 or Q3 and Q4 open and close in synchronization with the reference oscillation same wave number of the inverter circuit (
In FIG. 8(C)), the step-up ratio of the step-up transformer T1 is high and under non-braking conditions, and when the switching frequency is high, an oscillatory response occurs. The direction of flow of the oscillating [U changes at the zero cross point, and returns to the power supply side via the route of diode D2 - current transformer CTl - primary coil of step-up transformer T1 - diode D1. CT1 is the inverter circuit current (Fig. 8 (C)
) for monitoring, and the detection output is from the bridge rectifier circuit DB1.
The signal is full-wave rectified by , and the signal shown in FIG. 8+d) is obtained.

Furthermore, it is compared with the reference voltage Er by comparison 15Ic1 to obtain the output shown in FIG. 8(e). Due to the differential circuit of Cd and Rd, when the voltage in Fig. 8(e) becomes lower than the base * One signal is generated.Flip-flow is applied to J-, and the J terminal of the IC5 is at a low level as shown in FIG. 8(g), and the K terminal is at a high level as shown in FIG. 8(h). IC5 by the preset signal (Fig. 8 (i)) with the same amount as the reference oscillation waveform of
The Q terminal of is reset every half cycle and is at high level. Fig. 8(J) (kl is the drive signal of Ql, Q2 and Q3, Q4, respectively, synchronized with the reference oscillation waveform of Fig. 8(b).The trigger signal of Fig. 8(f) is I
When the CKi terminal of C5 is entered, the Q terminal of IC5 immediately becomes ro.
ve level, the outputs of IC3 and IC4 of the gate 1-ICs both become low level, and the transistors Q1. Q2
And Q3 and Q4 become open circuits. In this way, similar operations are repeated every half cycle to achieve high frequency switching. High DC voltage using a step-up transformer with a high step-up ratio according to the present invention! Since the conversion frequency of the source circuit can be increased, the response speed can be increased and the size can be reduced.

[Brief explanation of drawings]

1 to 5 are conventional circuit diagrams, FIG. 6 is a characteristic diagram thereof, and FIG. 7 and FIG. 8 are circuit diagrams of an embodiment of the present invention and operation waveform diagrams of each part thereof. In the figure, 1 is a rectifier circuit, 2 is an inverter circuit section 3, TI is a step-up transformer, and 4 is a high voltage
Flow circuit 6, C0NT is a control circuit section. Patent applicant Shindengen Kogyo Co., Ltd. Item 1 No. 30 Gi ÷ 9

Claims (1)

[Claims] A rectifier circuit that rectifies AC input into DC, an inverter circuit that converts the rectified output into high-frequency AC, a step-up transformer, a high-voltage rectifier circuit, and a control section that controls the inverter circuit on the primary side of the step-up transformer. A high-frequency DC high-voltage power supply circuit, characterized in that the control unit controls a switch element of the inverter circuit unit to close based on a signal that detects a zero crossing of an inverter circuit current.