High Power Supply Abnormal Load Detection Circuit
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Solution Overview
Problem
Conventional high power supplies in image forming apparatuses, such as laser printers, fail to safely interrupt high voltage output when an abnormal load is applied, posing safety risks due to human resistance or ground shorts, leading to potential electric shocks and circuit damage.
Innovation Solution
A high power supply with a single chip amplifying circuit that includes a load detector and controller to compare load voltage with a reference value, interrupting the high voltage output when an abnormal load is detected, using a high voltage power processor, trans/rectifier, and feedback unit to ensure safe operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high voltage is continuously output to ensure image forming capability, then image formation functionality is maintained, but safety risk increases when abnormal load is applied
Solution Approach 1:
The load detecting sensor is configured to detect abnormal loads before they can cause damage. The sensor monitors the load condition continuously and triggers the amplifying circuit to stop operation when an abnormality is detected, preventing electric shock or circuit damage before it occurs.
Solution Approach 2:
A load detecting sensor is introduced as an intermediary component between the high voltage output and the control system. The sensor detects abnormal loads and converts this information into signals that control the amplifying circuit, enabling safe operation without requiring complex direct monitoring of high voltage conditions.
2Reliability
If load detecting sensor and control circuit are added to detect abnormal load, then safety is improved, but device complexity increases
Solution Approach 1:
The load detecting sensor is integrated into the existing high power supply circuit structure. The sensor shares the same circuit board and power supply system, and its output directly controls the existing amplifying circuit stop function, merging the safety feature into the原有 system rather than adding completely separate monitoring equipment.
3Reliability
If amplifying circuit is interrupted to prevent electric shock, then safety is improved, but image forming capability is lost during abnormal condition
Solution Approach 1:
The abnormal load condition, which could cause electric shock or circuit damage, is converted into a useful control signal. The load detecting sensor transforms the harmful abnormal condition into information that automatically stops the amplifying circuit, preventing damage while maintaining system integrity for future operation.
Solution Approach 2:
The load detecting sensor provides continuous feedback about the load condition to the control system. When an abnormal load is detected, this feedback signal triggers the amplifying circuit to stop operation, creating a closed-loop safety mechanism that automatically responds to changing conditions.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Effectively prevents electric shocks and circuit damage by safely interrupting high voltage output when an abnormal load is detected, ensuring user safety and apparatus integrity during abnormal situations like removing the developing unit from the image forming apparatus.
Implementation Method 1
a load detecting sensor which detects an abnormal load at an output terminal when the abnormal load is applied to the output terminal by a human resistance or a ground (GND)
Implementation Method 2
an amplifier (OP-AMP) unit 130 which generates an input signal to a transformer 140 in order to control a level of an output voltage
Implementation Method 3
The transformer 140 turns on a driving transistor (TR2) according to a signal from the input unit 120. The transformer 140 controls a base current of the driving transistor TR2 to control a time constant and an output level of an oscillatory circuit at an input side of the transformer and to generate an AC type voltage at an output side of the transformer
Implementation Method 4
The rectifier 150 includes diodes D1 and D2 and capacitors C2, C3, and C4, receives the AC type voltage from an output side of the transformer 140 and generates a DC type voltage
Data Source
AI summary
A high power supply to control an abnormal load includes a high voltage power processor to amplify a supplied DC power and to output the amplified DC power, a trans/rectifier to transform the DC power to a high voltage power and to rectify the high voltage power, a load detector to compare a load voltage output from a load with a predetermined reference voltage and to output a comparison voltage to detect the abnormal load of the load, and a high voltage controller to supply a chip enable signal to the high voltage power processor to interrupt the high voltage power processor when the comparison voltage output from the load detector is smaller than a predetermined reference value that is set to correspond to a minimum load of the load. Therefore, a user and peripheral components an image forming apparatus are protected from electric shock and being damaged by interrupting an output of the high voltage according to the abnormal load.