| 摘要 |
A converter which converts mains frequency electrical power into a higher frequency power, which is more desirable for driving gas discharge lamps. The converter comprises a half-bridge inverter (Q1 and Q2) connected across a filter capacitor (C3) of a filtered, rectified supply, which is effectively isolated from the rectifier (D1-D4) at mains frequency by isolating diodes (D5, D6) which are reverse biased for the majority of the mains frequency cycle, when the filter capacitor (C3) is fully charged. The isolation diodes (D5, D6) are bypassed by capacitors (C4, C5) at the switching frequency of the inverter such that a proportion of the inverter output current is drawn directly from the supply rather than from the filter capacitor (C3). The return path for the inverter output current is via the AC divider network (C1, C2). An inductance L1 is provided to limit current to the lamp (P), while a capacitor (C6) is provided in series with the heaters of the lamp (P) to provide a heating current during starting. According to another feature of the invention, a switching regulator is provided wherein a switching regulator control circuit (SRCC) drives the Switching element (Q2) of a switching regulator circuit and the frequency of the output of the Switching Regulator Control Circuit (SRCC) is controlled to maintain the output voltage (M) of the switching regulator at a substantially constant level, while the pulse width of the output from the Switching Regulator Control Circuit (SRCC) is controlled in response to the instantaneous rectified supply voltage (N) such that the current (I) drawn by the regulator is substantially sinusoidal. |
