【单选题】【消耗次数：1】
降压斩波电路中，已知电源电压 Ud=16V，负载电压 Uo=12V，斩波周期 T=4ms，则开通时 Ton=（ ）
①
1ms
②
2ms
③
3ms
④
4ms
参考答案：
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