diff --git a/include/libopencm3/stm32/l4/pwr.h b/include/libopencm3/stm32/l4/pwr.h
index a3219988..f4d2b911 100644
--- a/include/libopencm3/stm32/l4/pwr.h
+++ b/include/libopencm3/stm32/l4/pwr.h
@@ -169,7 +169,7 @@ enum pwr_vos_scale {
 
 BEGIN_DECLS
 
-/* TODO */
+void pwr_set_vos_scale(enum pwr_vos_scale scale);
 
 END_DECLS
 
diff --git a/lib/stm32/l4/Makefile b/lib/stm32/l4/Makefile
index f67c6db1..041b335d 100644
--- a/lib/stm32/l4/Makefile
+++ b/lib/stm32/l4/Makefile
@@ -37,7 +37,7 @@ TGT_CFLAGS      += $(DEBUG_FLAGS)
 ARFLAGS		= rcs
 
 # Specific objs
-OBJS		= adc.o
+OBJS		= adc.o pwr.o
 
 # common/shared objs
 OBJS            += rcc_common_all.o
diff --git a/lib/stm32/l4/pwr.c b/lib/stm32/l4/pwr.c
new file mode 100644
index 00000000..7bfc8361
--- /dev/null
+++ b/lib/stm32/l4/pwr.c
@@ -0,0 +1,55 @@
+/** @defgroup pwr_file PWR
+ *
+ * @ingroup STM32L4xx
+ *
+ * @brief <b>libopencm3 STM32L4xx Power Control</b>
+ *
+ * @version 1.0.0
+ *
+ * @author @htmlonly &copy; @endhtmlonly 2016 Benjamin Levine <benjamin@jesco.karoo.co.uk>
+ *
+ * @date 4 March 2013
+ *
+ * This library supports the power control system for the
+ * STM32L4 series of ARM Cortex Microcontrollers by ST Microelectronics.
+ *
+ * LGPL License Terms @ref lgpl_license
+ */
+/*
+ * This file is part of the libopencm3 project.
+ *
+ * Copyright (C) 2016 Benjamin Levine <benjamin@jesco.karoo.co.uk>
+ *
+ * This library is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this library.  If not, see <http://www.gnu.org/licenses/>.
+ */
+/**@{*/
+#include <libopencm3/stm32/pwr.h>
+
+void pwr_set_vos_scale(enum pwr_vos_scale scale)
+{
+	uint32_t reg32;
+
+	reg32 = PWR_CR1;
+	reg32 &= ~(PWR_CR1_VOS_MASK << PWR_CR1_VOS_SHIFT);
+	switch (scale) {
+	case PWR_SCALE1:
+		reg32 |= (PWR_CR1_VOS_RANGE_1 << PWR_CR1_VOS_SHIFT);
+		break;
+	case PWR_SCALE2:
+		reg32 |= (PWR_CR1_VOS_RANGE_2 << PWR_CR1_VOS_SHIFT);
+		break;
+	}
+	PWR_CR1 = reg32;
+}
+/**@}*/