JPS5910168A - High voltage power source - Google Patents

Abstract

PURPOSE:To enable to reduce the size, weight and noise and to increase the efficiency of a high voltage power source and to stably supply by a transformer high and low voltage to a load by detecting the load current and constantly controlling a load current with a detection signal. CONSTITUTION:A flyback transformer T1 has a plurality of high and low voltage output coils. Power supply circuits 2-1, 2-2 to a high voltage load and a power supply circuit 2-3 to a low voltage load are provided at the secondary side of this transformer T1. An error amplifier Q1 compares a reference voltage applied to a terminal P3 with the voltage detected by a sampling resistor R3, thereby controlling the coil voltage at the primary side of the transformer T1. As a result, the output waveform of the terminal P1-1 is stabilized, thereby maintaining the load current of the load connected to the terminal P1-1 accurately at the constant current.

Description

[Detailed description of the invention] The present invention relates to a high voltage power supply device.

Conventional devices of this type include those using an iron resonant transformer, and those using a self-excited inverter or a separately excited inverter. However, high-voltage power supplies that use iron-resonant transformers have drawbacks such as being large and heavy, while high-voltage power supplies that use self-excited or separately excited inverters have the drawbacks of high switching loss and high noise. Was. Furthermore, when such a high-voltage power supply is used to drive multiple chargers in a copying machine, for example, one transformer must be used for each charger that requires constant current drive. Ta. Furthermore, in addition to the high-voltage winding for the charger, a plurality of transformers had to be used to supply power to low-voltage loads such as those for developing bias and sequence control.

The present invention has been made in view of the above points, and it is an object of the present invention to provide a small and lightweight high voltage power supply device.

The present invention also provides a high-voltage power supply device with high efficiency and low noise.

Another object of the present invention is to provide a high-voltage power supply device that can stably supply power to high-voltage and low-voltage loads using one transformer.

(This provides a high-voltage power supply device that can maintain a constant current of .

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a configuration example of a high-voltage power supply device for explaining the present invention. In the figure, Tl is a flyback transformer, 2 is a high voltage rectifier circuit, 3 is a load current detection circuit, 4 is an oscillation circuit, 1
is the power regulation circuit. Below, items that perform the same actions are given the same number.

The circuit will be explained. The switching transistor Tr+ is repeatedly turned on and off by the output signal of the oscillation circuit 4. The flyback transformer T1 stores energy when the switching transistor Tr+ is on, and stores the energy when the switching transistor Tr+ is off using the inductance seen from the primary side, the distributed capacitance of the flybank transformer T+ seen from the primary side, and the external capacitor (resonant capacitor).
C Further, the value of the leakage inductance of the flyback transformer T1 is set so as to resonate with the distributed capacitance at a higher frequency to improve efficiency. The power adjustment circuit 1 controls the voltage applied to the primary side or the energization time to the primary side in order to keep the load current detected by the load current detection circuit 3 constant.

Figure 2 shows signal waveforms at each part. Here, A is the oscillation circuit 4
The output signal of the switching transistor Tr+
pace drive signal, the switching transistor Tr
+ collector voltage waveform, C is flyback transformer Tl
2 is the output waveform of the O secondary winding, and 2 is the collector current waveform of the switching transistor Tr+. Furthermore, if there is no damper diode I)l, the collector voltage waveform will be as shown by the broken line at the signal waveform opening. damper diode DI
is conductive during the negative cycle of the switching transistor Tr+, and serves to protect the switching transistor Tr+ and return energy to the power adjustment circuit 1. Further, since the output waveform (signal waveform c) of the secondary winding of the flyback transformer T+ becomes long, the rectified output voltage can take almost the full amplitude. At the beginning of the signal waveform, the collector voltage rises as a sine wave when the switching transistor Tr+ is off. Therefore, switching loss at this time is small and efficiency is high. Furthermore, when the switching transistor Tr+ is on, the collector current is close to zero volts, so the loss at this time is also very small. Regarding noise, the collector voltage waveform is a sine wave as shown in the signal waveform section, and the collector current waveform is a linearly increasing waveform as shown in the signal waveform section, so high frequency noise is extremely reduced.

Furthermore, by lengthening the on-time of the switching transistor Tr+, a considerable boost can be achieved on the primary side, and the rectified output voltage can reach almost its peak value, making it possible to reduce the boost ratio of the flyback transformer T1. In this embodiment, the step-up ratio of the transformer can be reduced to 1/10 to 1/20. Therefore, the flyback transformer T+ can be made smaller and lighter. Further, since the output waveform of the secondary winding is outputted as shown in the signal waveform C, the reverse withstand voltage of the diode in the high voltage rectifier circuit 2 can be small. Therefore, if the device is constructed as shown in FIG. 1, a high voltage power supply device with low noise and high efficiency can be obtained.

FIG. 3 is an example showing the high voltage power supply device of FIG. 1 in more detail. Here, voc and vgg are input power supply voltages, and the same applies to other figures below. In FIG. 3, the load current and the sampling resistor R3 in the current detection circuit 3 produce a voltage v3. Power adjustment circuit 1
The error amplifier Q+ within the terminal P3 compares the reference voltage applied to the terminal P3 with the voltage v3 to control the primary winding voltage of the flyback transformer TI. As a result, the output waveform of the secondary winding is stabilized and constant current characteristics are maintained. Furthermore, since the device shown in FIG. 3 is highly efficient as described above, the loss in the power adjustment circuit J for constant current control can be relatively small.

Although the power control circuit 1 in FIG. 3 is composed of a series regulator, it can also be composed of a self-excited switching regulator as shown in FIG. 4 to control the energization time.

In FIG. 4, error amplifier Q2 operates as a comparator, and transistors Ty3 and Tr4 operate as switching transistors.

FIG. 5 shows an embodiment of the high voltage power supply device of the present invention. In the figure, the flybank transformer T1 has a plurality of high voltage output windings and low voltage output windings. Here, 2-] and 2-2 are power supply circuits for different high-voltage loads, and 2-3 is a power supply circuit for various low-voltage loads such as those for sequence control. Also LE
Dl is a diode for indicating high voltage generation for maintenance. @
In particular, the circuit shown in FIG. 5 is configured to keep the load current of the load connected to terminal PI-1 constant. In this case, the load current of the load connected to the terminals P1-2 will be affected by the load characteristics of the load connected to the terminals P+-+.

The error amplifier Q1 compares the reference voltage applied to the terminal P3 and the voltage detected by the sampling resistor R3, and calculates the primary winding voltage (applied voltage) of the flyback transformer T+0.
control. As a result, the output waveform of the terminal P1-1 is stabilized, and the load current of the load connected to the terminals p+-+ can be maintained at a constant current with high precision.

As described above, if the device is configured as shown in FIG. 5, the efficiency is high, and the loss in the power adjustment circuit 10 for constant current control can be relatively small.

If the high-voltage power supply device shown in Fig. 5 is used for a copying machine f, for example, a predetermined charger that requires a highly accurate and constant load current is connected to the terminal P+-+, and the other chargers are connected to the terminal P+. -2. Also, the terminals p+-s can be connected to various low-voltage loads such as development bias, sequence control, and display.In this way, one transformer can stably handle high-voltage and low-voltage loads. Since the power supply can be carried out, a compact and lightweight copying machine can be obtained.

In this embodiment, the power adjustment circuit 1 is configured to control the voltage applied to the primary side of the flyback transformer T1.
It is possible to use the power adjustment circuit 1 that controls the energization time.
. In this case, the power loss of the power adjustment circuit 1 can be significantly reduced.

For this reason, we have further reduced the size and weight of the entire high-voltage power supply,
Since the allowable fluctuation range of the input power supply voltage Voo can be widened, the temperature rise of other related devices can be suppressed.

As explained above, according to the present invention, it is small, lightweight, highly efficient, and
A low-noise high-voltage power supply device can be provided. Also 1
A single transformer can provide stable power supply to high-voltage and low-voltage loads.

Furthermore, it is possible to provide a highly reliable high-voltage power supply device that can maintain the load current of a predetermined load among a plurality of loads at a constant current with high precision.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of the configuration of a high-voltage power supply device for explaining the present invention, and FIG. 2 is an operational waveform diagram of each part of FIG. 1.
Figure 3 is a specific circuit diagram of the high-voltage power supply shown in Figure 1;
The figure is a circuit diagram of a high-voltage power supply using a switching regulator, and FIG. 5 is a circuit diagram of the high-voltage power supply in this embodiment. Here, T1 is a fly bank transformer, 1 is a power adjustment circuit, 2 is a high voltage rectifier circuit, 3 is a 9-charge current detection circuit, 4 is an oscillation circuit, Dl is a diper diode, Trl is a switching transistor, and Ql and Q2 are error amplifiers. be.

Claims (1)

[Claims] A transformer that outputs at a predetermined number of circumferences and has a high-voltage output winding and a low-voltage output winding, a load current detection circuit that detects the load current, and a detection signal from the load current detection circuit to keep the load current constant. A high-voltage power supply device comprising a power adjustment circuit for controlling the power.