Energy feedback circuit for electronic printers - incorporates transistorised switch circuit and synchronised back-up energy pulse to stabilise feedback energy levels

摘要

An AC supply voltage (1) is rectified (2) and the ripple removed through capacitors (3). An oscillator (4) is controlled by a control input (5) and generates a high frequency AC supply which is transformed (6) (7) and rectified (9) (11) to form the power supply to an electromagnet (14) operating an ink-jet or pen. The switch (13) connects the energy contained in the electromagnet to a buffer capacitor (16). The charge is fed back to secondary transformer circuit (8) via a freewheeling diode (15). To maintain energy levels when the magnet coil is discharged alternative pulses are obtained via a control signal (12) which drives an auxiliary switching transistor (10) in synchronism with main rectifier (9) conducting period. This results in energy also being supplied to the transformer secondary circuit (8).