An adaptive constant average voltage output circuit
In order to solve the problem of low efficiency of LDO and peripheral capacitors or inductors of DC-DC in the electronic igniter applications,an adaptive constant average voltage output circuit was proposed.The circuit output produced a PWM wave and a constant average voltage output was achieved by automatically adjusting the duty cycle of the PWM wave in response to variations in the power supply voltage.The average output voltage can be adjusted by changing the proportion of the external sampling resistors.The circuit is operated in open-loop with simple and feasible feature,and no close-loop stability consideration is needed.Meanwhile,it achieves high efficiency that comparable with DC-DC,but without peripheral inductors and capacitors,so the integration and miniaturized applications was facilitated.The circuit was designed with 0.18 μm BCD process.The simulation and test results show that under the power supply voltage of 3.2-4.2 V,a constant average output voltage can be achieved with an error of less than±1%;By changing the sampling resistance ratio,the average output voltage can be continuously adjusted within 1.5-3.6 V.
constant average voltageadaptive duty cyclePWMopen-loop controlcapacitance-and-inductance-free
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